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can

/ˈkæn/

Auxiliary verb meaning be able to; know how to.

From O.English / Proto-Germanic cunn (to know).

verb
noun
cunn
Proto-Indo-European
Verified
*gno-
reconstructed
to know

from PIE root *gno- "to know." It holds now only the third sense of "know," that of "know how to do something" (as...

Proto-Germanic
Verified
*kunnjanan
reconstructed
be mentally able; have learned

from Proto-Germanic *kunnjanan "be mentally able, have learned" (source also of Old Norse kenna "become acquainted,...

Old English
AI-inferred
cunnan
to know, know how; later also 'be able to'
Modern English
AI-inferred
can
surviving auxiliary, chiefly expressing ability or permission
Modern English
AI-inferred
can → could
past form preserved as the everyday preterite
Modern English
AI-inferred
couth / uncouth
relics of the older participle and its negation
Modern English
can

Some of the smallest words in English have the longest memories. This little helper started out as Old English cunnan, a verb about knowledge and skill — not abstract facts, but the practical kind, the sort you need to thread a needle or survive a winter. That’s why it sits beside cousin words like could, couth, uncouth, and even cunning: the family tree is full of people who either know their business or don’t. The trail runs back through Proto-Germanic *kunnjanan to the very old PIE root *gno-, the same ancient backbone that gave Latin cognoscere and Greek forms of knowing. So every time you say “I can,” you’re using a fossilized fragment of an old boast: not just “I exist,” but “I know how.”

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