Glossary

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Protocol: JustLend DAO (Compound V2 fork on TRON) · Network: TRON Mainnet (semantics carry over to Nile testnet) · Scope: definitions, units, and on-chain encoding of every protocol-specific term used elsewhere in this documentation. Each entry links to the function that returns or sets the value where applicable.

Terms are grouped by what they describe. Within each group, entries are ordered alphabetically. All scaled values use base-1e18 unless explicitly noted.

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Units of value

sun

The smallest indivisible unit of TRX on TRON. 1 TRX = 10⁶ sun (TRX has 6 decimals). All TRX amounts that cross a contract boundary — msg.value, transfer() amounts, the Price Oracle's denominator — are in sun. The JustLend public HTTP API de-scales TRX amounts back to human-readable TRX (see *InTrx fields in APIs §1.3; see also §1.4 Rate / APY semantics).

mantissa

A fixed-point integer scaled by 1e18. Compound V2 (and JustLend) represents fractional values like rates, factors, and exchange rates as uint256 mantissas to avoid floating-point. To convert a mantissa back to a human decimal, divide by 1e18. Examples:

• collateralFactorMantissa = 800000000000000000 → 0.80 → 80% collateral factor.
• liquidationIncentiveMantissa = 1080000000000000000 → 1.08 → 8% liquidator reward.
• exchangeRateMantissa = 200000000000000000000000000 (2e26), with an 18-decimal underlying and an 8-decimal jToken: 1 jToken = 2e26 / 10^(18 + 18 - 8) = 0.02 underlying tokens. Dividing the mantissa by 1e18 alone gives a ratio of raw units, not a ratio of whole tokens.

A "scaled by 1e18" annotation anywhere in this documentation means "this is a mantissa."

jToken decimals

jTokens always use 8 decimals, regardless of the underlying's decimals. So balanceOf(account) on a jToken returns a number in units of 10⁻⁸ jToken. redeem(redeemTokens) takes its argument in those same 8-decimal units. redeemUnderlying(redeemAmount) takes its argument in the underlying's own decimals.

underlying decimals

Each TRC20 underlying carries its own decimals() value. JustLend markets currently span:

Underlying	decimals
TRX (native)	6
USDT, USDC, NFT, WIN, WBTT	6
BTC, WBTC	8
USDD, ETH, ETHB, TUSD, USDJ, USD1, SUN, BTT, JST, HTX, sTRX, wstUSDT	18

For machine consumers, /developers/contracts.json → networks.*.jtokens.<symbol>.underlying_decimals carries the canonical per-market value.

The sTRX, wstUSDT, TUSD, USDJ, USD1, SUN, BTT, JST, HTX, and WBTT values above were checked against their Mainnet decimals() calls on 2026-10-12. The linked registry includes each underlying contract address; do not apply a mainnet value to an unrelated token with the same symbol.

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Interest rate model

borrowRatePerBlock / supplyRatePerBlock

The per-block interest rate the market currently charges borrowers (and pays suppliers, net of reserves). Mantissa-scaled (1e18). To convert to APY:

APY ≈ borrowRatePerBlock / 1e18 × blocksPerYear
blocksPerYear ≈ 10,517,760 on TRON at ~3 s/block (365.25 × 86400 / 3)

For precision, prefer the API's pre-computed apy / supplyRate / borrowRate fields — they already account for compounding and the current block cadence. See APIs §1.4.

borrow index

A monotonically increasing per-market uint256 that records cumulative interest factor. Stored on the jToken contract. A borrower's outstanding balance at any time is principalBalance × currentBorrowIndex / borrowIndexAtPrincipalSnapshot. You normally don't compute this manually — call borrowBalanceCurrent(account) and let the contract do it.

kink

The utilization rate at which the JumpRateModelV2 switches from the gentle linear segment to the steep linear segment. Mantissa-scaled. Typical value 0.8e18 = 80% utilization. Below the kink, borrowRate(u) = a₁ × u + b. Above the kink, borrowRate(u) = a₁ × kink + a₂ × (u − kink) + b.

utilization rate (u)

u = borrows / (cash + borrows − reserves)

Ranges from 0 (no borrowing) to 1 (every supplied unit is currently borrowed). Drives both borrowRatePerBlock and supplyRatePerBlock in real time. See Interest Rate Model.

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Risk parameters

borrow cap

A per-market maximum on totalBorrows, set by Governance to limit exposure to a single asset. Distinct from borrow limit (which is per-account). Borrow caps can be inspected on the Comptroller; when a cap is reached, borrow() reverts with a COMPTROLLER_REJECTION error.

borrow limit

The maximum total value (in TRX-equivalent or USD-equivalent) a single account can borrow given its current collateral:

borrowLimit = Σᵢ (suppliedAmountᵢ × oraclePriceᵢ × collateralFactorᵢ)
            over markets i the user has entered via enterMarkets

Distinct from borrow cap. Computed implicitly inside getAccountLiquidity(account) on the Comptroller — liquidity is borrowLimit − totalBorrowValue.

close factor

The maximum fraction of a borrower's outstanding debt in the selected borrowed market that one liquidateBorrow() call may repay, not a fraction of debts summed across different assets. Mantissa-scaled. JustLend currently uses 0.5e18 → 50%. Read via Comptroller.closeFactorMantissa(). A later liquidation requires a fresh eligibility check; one liquidation may already restore the account's collateral coverage.

collateral factor

The fraction of a supplied asset's value that the protocol counts toward the user's borrow limit. Mantissa-scaled, in [0, 0.9e18]. Set by Governance per market. A 0.80 factor means $100 supplied → $80 toward your borrow limit. Read via Comptroller.markets(jToken).collateralFactorMantissa.

liquidation incentive

The bonus a liquidator receives — paid by seizing extra collateral above the debt being repaid. Mantissa-scaled. JustLend currently uses 1.08e18 → 8% reward (the liquidator receives 1.08× the repaid debt value in collateral). Read via Comptroller.liquidationIncentiveMantissa().

reserve factor

The fraction of accrued interest that the protocol retains as reserves rather than passing through to suppliers. Mantissa-scaled, per-market. A reserveFactor of 0.1e18 means 10% of borrower interest is held as reserves; 90% flows to suppliers. Read via <jToken>.reserveFactorMantissa(). Changed by Governance only.

Risk Value

JustLend's user-facing single-number health metric. Defined on the dApp and on the Liquidations page:

RiskValue = totalBorrow / borrowLimit × 100

A display ratio, defined when the borrow limit is positive. Debt above that limit corresponds conceptually to RiskValue > 100; the authoritative V1 undercollateralization check is a successful getAccountLiquidity(account) read with shortfall > 0. Display rounding, oracle values, and integer arithmetic can affect the boundary. A displayed 100 is not proof of eligibility; see boundary examples.

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Token mechanics

exchange rate (jToken ↔ underlying)

The ratio used by mint/redeem to exchange jTokens for the underlying. Supply interest is reflected in the exchange rate, rather than an increase in the holder's jToken balance. Do not assume a universal initial rate or a 1:1 whole-token ratio.

underlying raw units = jToken raw units × exchangeRateMantissa / 10^18
underlying tokens per 1 jToken = exchangeRateMantissa / 10^(18 + underlyingDecimals - 8)

For example, 2e26 with an 18-decimal underlying means 0.02 underlying tokens per jToken. A hypothetical rate of 0.02e18 gives 10^8 × 0.02e18 / 10^18 = 2,000,000 underlying raw units per whole jToken; with a 6-decimal underlying that is 2 underlying tokens, not 50 raw units.

Use integer arithmetic for raw amounts (division rounds down):

function underlyingRawFromJTokens(jTokenRaw, exchangeRateMantissa) {
  return BigInt(jTokenRaw) * BigInt(exchangeRateMantissa) / (10n ** 18n);
}

Read via <jToken>.exchangeRateCurrent() (accrues interest first) or exchangeRateStored() (cached). Convert the resulting raw amount using the underlying's own decimals.

exchange rate (sTRX ↔ TRX)

The current ratio at which deposit/withdraw exchange sTRX for TRX. Mantissa-scaled to 1e18. Always ≥ 1 (no initial premium), monotonically increases as voting + Energy-Rental rewards accrue. Read via sTRX.exchangeRate().

redemption ratio

Same concept as exchange rate but used colloquially to mean "how much underlying I get back per whole share." For jTokens use exchangeRateMantissa / 10^(18 + underlyingDecimals - 8); for sTRX the whole-token TRX-per-sTRX ratio is exchangeRate() / 1e18 (raw TRX and sTRX amounts still have different decimals).

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Governance

Vote (1 JST = 1 Vote, after WJST wrap)

Voting power is token-weighted, not one vote per holder: deposit JST into WJST 1:1, with both amounts represented in 18-decimal raw units. The current WJST implementation uses the voter's available balance at voting time, not a proposal-block balance snapshot; the additional weight cast is locked for that proposal. When the proposal is no longer Pending or Active, call WJST.withdrawVotes(proposalId) to unlock it, then WJST.withdraw(amount) to redeem available WJST for JST. Neither step is automatic. See Governance: available votes and withdrawal.

proposal threshold

The available WJST balance gate for propose(): a non-whitelisted account must have strictly more than 200,000,000 WJST, not exactly that amount or merely JST in its wallet. A current whitelist entry bypasses this gate, not other proposal checks. proposalThreshold() = 2e26 raw units was read on 2026-10-14; see governance boundaries and evidence.

quorum

The inclusive minimum For-votes: For votes >= 600,000,000, together with the separate strict condition For > Against. Exactly 600,000,000 meets quorum, but a tie with Against fails. quorumVotes() = 6e26 raw units was read on 2026-10-14. See governance boundaries and evidence.

Timelock

The 48-hour minimum delay between queueing a successful proposal and execute() becoming callable. Enforced by a separate Timelock contract (TRWNvb15NmfNKNLhQpxefFz7cNjrYjEw7x), the only address authorized to call privileged setters on JustLend contracts.

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Market status

active (jToken status)

Open for new supply and borrow. The default state. 18 of 24 jToken markets are currently active.

legacy (jToken status)

Closed to new supply and borrow. Existing positions can still be unwound (repayBorrow, redeem, redeemUnderlying). The contract remains queryable indefinitely; addresses do not get reused. 6 of 24 jToken markets are currently legacy. The canonical list and per-market status field are in contracts.json and the APIs §2 reference table. See also: Developer common pitfalls — legacy markets.

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External primitives

Multicall3

A widely-deployed contract that lets callers bundle many read-only EVM/TVM calls into a single transaction-less RPC request, dramatically reducing round-trip overhead when fetching state across N markets / accounts. On TRON Mainnet, Multicall3 is deployed at TX56WKxtja91Dybf2FdN4hZbDLyKVxxhAu (verified on-chain — contract name is literally Multicall3). The JustLend MCP server uses it to query all jToken markets in a single round trip; see MCP Server → Account & Balances. For your own integrations, the canonical Multicall3 ABI works as-is; no protocol-specific wrapper needed.

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Where to look next

• APIs §1 — concrete API field semantics referencing the same terms.
• SBM reference — full function-signature reference for the jToken contract.
• Common pitfalls — gotchas that bite even when terms are understood correctly.
• /llms-full.txt — single-file snapshot for one-shot LLM ingestion.

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