Read the rule before answering
Choose a unit from the seven-row SI base-unit table. A physical quantity, a derived unit or a prefixed alternative does not add an extra row to that table.
Six untimed questions, starting with this one.
Check an answer here
Check this question’s accepted set without submitting to a game or opening the full answer list.
Only your submitted spelling will be checked. Other answers stay hidden.
Read the lesson — reveals answers & strategy
Understand the boundary
The seven base units are second, metre, kilogram, ampere, kelvin, mole and candela. A base quantity such as length is not a unit name. Derived units such as newton and prefixed alternatives such as centimetre do not enlarge this seven-entry set.
Verify the facts: BIPM · SI base units ↗
Choose an answer for your goal
Our explicit aliases make symbols useful inputs, but the catalog is not a general unit parser. Look up a symbol in this question’s accepted list before using it. Case normalization here is an input convenience, not a statement that symbol capitalization is interchangeable in scientific notation. Choose a unit you can identify and spell, then use its fixed points to set your training goal.
Worked examples — reveals answers
- kg · Accepted
- An explicit alias for kilogram, the SI base unit of mass.
- newton · Outside this set
- A derived SI unit rather than one of the seven base units.
- mass · Outside this set
- A physical quantity; the question asks for a unit.
Practice the distinction
Pair one quantity with its base unit, then submit only the unit. Check a derived unit next and explain the mismatch. This practices recognition rather than memorizing seven disconnected words.
Try it in the checker ↑Give me a hint — no answer revealed
Start with the full category, then apply the exact boundary: Base units only. Unit names, plurals and symbols are accepted. You only need one qualifying answer. A longer name is not automatically rarer.
Reveal a verified practice pick
This pick belongs to the selected question’s answer set. Points are a fixed knowledge rating.
Reveal a fast high-scoring answer
Shortest accepted input at 65+ points
AAmpere · 68 points · 1 characters
Ampere is one of the seven SI base units defined by the International Bureau of Weights and Measures.
Highest fixed score
Candela98 points · Shortest accepted spelling: cd
These are editorial points, separate from real player choice counts.
Reveal all 7 practice answers
Filter by a name or listed alias. Scores are fixed knowledge ratings.
7 accepted answers
No answers match these filters. Try another spelling or a lower minimum score.
What players actually choose
– UTC · 469 recorded daily rounds. Source: Krillionio daily submissions. Skips and timeouts are included in the denominator; practice and Battle are excluded.
140 / 469 rounds ended with an accepted answer (29.9%). Average: 14.7 fixed points.
Compare observed choices — reveals answers
Question quality signals
These measurements cover completed daily rounds recorded with timing and rejection details. Older rounds without those fields are excluded. At least 20 measured rounds are required per question.
Review thresholds: below 20% accepted, at least 40% timed out, or at least 30% of rounds with an unlisted input. These flags suggest checking the wording and answer coverage; they do not prove an answer is wrong or change points automatically. Abandoned rounds and practice attempts are not included.
How these statistics work
- What is counted
- Source: Krillionio daily submissions. Skips and timeouts count as rounds; practice and Battle are excluded.
- When comparisons appear
- A question needs at least 20 recorded rounds. An answer also needs at least 5 recorded choices within that question.
- What the data can tell you
- These anonymous browser records are not verified unique people or a representative survey. The player rarity index does not change game points or predict the original Krillion game. Raw submissions stay private.
Rule examples & common mix-ups — may reveal answers
- Base units and derived units are different sets. Follow any symbol-length restriction in the question; adding a metric prefix does not create another base unit.
These notes explain the question boundary; they are not a ranking of player mistakes.
Why these answers qualify
Each entry belongs to the bounded set defined by the prompt. The named source supports the underlying facts; our editorial scoring is a separate layer.
Source: BIPM · SI base units ↗
Reference version: 2026-09-13. See our answer policy for how we handle aliases and omissions.