The Lemma Glossary.
Every term used on the platform, defined plainly. No jargon without explanation.
Adaptive Assessment
An assessment that adjusts its difficulty in real time based on your answers. Get three correct in a row and the next question is harder; struggle and it recalibrates. Lemma's adaptive assessments ensure the score reflects your actual ceiling, not a lucky run.
Assessment
A structured evaluation of skill competence, conducted through peer sessions or employer-initiated checks via the Developer API. Assessments generate evidence events that contribute to SCI computation.
Canonical Skill Key
The single, authoritative identifier for a skill in the Lemma system. All references – user profiles, sessions, evidence events – resolve to canonical keys. This prevents fragmentation from aliases (e.g., 'React.js', 'ReactJS', and 'React' all resolve to one canonical key).
Endorsement
A peer's formal acknowledgment that they observed a specific skill being demonstrated. Unlike LinkedIn endorsements, Lemma endorsements are generated through real sessions and carry weight proportional to the endorser's own trust tier.
Evidence
Observable proof generated during peer sessions, assessments, or external integrations. Evidence is recorded as immutable events – once logged, it cannot be altered or deleted.
Focus Skill
The primary skill a user is actively developing on Lemma. The focus skill receives priority in matching recommendations and is prominently displayed on the skill passport.
Freshness Score
A component of the SCI formula (0–15 points) that measures the recency of your evidence. Older evidence decays to keep scores reflecting current ability rather than historical performance.
Immutable Evidence
Evidence that, once recorded, cannot be altered or deleted. Lemma uses an append-only event log for all skill evidence. Immutability ensures the audit trail is trustworthy.
LemmaCoins (LC)
The internal currency used to book peer sessions. You earn LC by completing teaching sessions and receive a monthly grant on the free tier. The LC economy is governed by versioned rules published in the platform docs.
Matching Engine
The algorithm that ranks potential session partners using 12 signals – skill tier gap, timezone overlap, session history, rating average, availability, communication style, learning pace, goal alignment, language, reliability score, teaching style, and mutual skill match. Zero self-reported data is used.
Onboarding
The initial flow that helps new users set their focus skill, understand their starting SCI, and book their first session. Onboarding is optimized to get new members to their first proof event within 48 hours.
Peer Session
A structured, time-boxed interaction between two practitioners where both demonstrate and evaluate skills. Sessions are the primary evidence-generating mechanism on Lemma.
Phase
A progress milestone within a skill's XP progression. Each skill progresses through phases as the user accumulates XP from sessions and assessments. Advancing a phase generates a proof event visible in the skill passport.
Practice Score
A component of the SCI formula (0–25 points) that reflects the volume of sessions completed and XP earned. More practice means more practice score – but not infinitely. The component is capped and normalized.
Proof Event
A specific, timestamped event in the evidence log representing a demonstration of skill – a session completed, a tier advanced, an assessment passed, a peer endorsement received. Proof events are the atomic unit of the skill passport's evidence trail.
Proof History
The chronological list of all proof events for a specific skill, visible on the skill detail page of a user's passport. Proof history lets employers trace exactly how a credential was earned, event by event.
Reliability Score
A component of the SCI formula (0–20 points) that measures session show rate, consistency of participation, and peer rating averages. Practitioners who frequently cancel or no-show see this component decrease.
SCI (Skill Credibility Index)
A computed score (0–100) representing how credible a person's skill claim is, based on accumulated peer session evidence. SCI is computed from four components: Practice (0–25), Proof (0–40), Reliability (0–20), and Freshness (0–15). The full formula is published at getlemma.io/methodology/sci-explained.
Session
On Lemma, sessions are the primary unit of learning and evidence generation. Each completed session contributes to both participants' SCI scores and skill passport histories. See: Peer Session, Teaching Session.
Skill Credibility Index
The full name for SCI. A quantitative measure of demonstrated skill competence, computed from peer session evidence, session quality signals, and consistency over time. The formula is open and versioned.
Skill Passport
A portable, verifiable record of all your demonstrated skills, including SCI scores, trust tiers, session history, and evidence events. Your Skill Passport is backed by the full immutable evidence log and can be shared via a permanent link.
Teaching Session
A peer session where the primary role is teaching rather than learning. Teaching sessions generate evidence for the teacher's Proof and Reliability components and earn LemmaCoins. The teaching record is visible on the skill passport as evidence of deep competence.
Trust Tier
A progression level reflecting the depth of verified evidence backing your skill claims. Tiers range from Newcomer through Learner, Proven, Verified, and Expert, to Authority. Each tier requires stronger evidence and unlocks new opportunities.
XP (Experience Points)
Experience points earned from completing peer sessions, passing assessments, and teaching. XP fuels progression through skill phases. Each action earns a defined number of XP points documented in the platform.