What does canst mean?
"Canst" is the archaic second-person singular present tense of the verb "can," used in earlier forms of English when addressing a single person addressed as "thou." Where modern English says "you can go," Early Modern English said "thou canst go," attaching the characteristic -st ending that also produced forms like "thou dost" and "thou knowest." The form is strongly associated with the King James Bible and Shakespeare's plays, appearing in famous lines such as "thou canst not then be false to any man." Although obsolete in contemporary speech, it remains familiar through scripture, literature, hymns, and liturgical language, so most English readers recognize it even if they never use it. Encountering "canst" is essentially an exercise in reading history: it signals an older register and a formal or intimate address between speaker and listener. For learners, it is best treated as a passive-recognition word — understood when read, but not reproduced except in deliberate imitation of period style.
verb"Canst" is the archaic second-person singular present form of the verb "can," used in older English when addressing one person as "thou." It means to be able to, to have the power, skill, or capacity to do something.
- Archaic second-person singular present of "can": to be able to, to have the ability or capacity to do something.
"Thou canst not serve two masters."
"Thou canst not pluck a flower without troubling a star."
"If thou canst keep thy word, thou shalt be greatly rewarded."
Shakespeare wrote it more than 2,500 times — "thou canst" is how the English language once said "you can," one letter away from modern "can't" in reverse.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of canst
"Canst" derives from Old English "cunnan," meaning "to know, to know how," which gave rise to the modal verb "can" and its inflected forms. In Middle and Early Modern English, verbs addressing the second person singular took the ending -est or -st, yielding "thou canst." As the pronoun "thou" fell out of general use by the seventeenth and eighteenth centuries in favor of "you," its accompanying verb forms, including "canst," became obsolete. It survives today chiefly in the fixed religious and literary language of the King James Bible and Shakespearean English.
How canst is actually used
"Canst" belongs exclusively to historical and literary English and is now obsolete in ordinary speech and writing. It appears in Early Modern English texts such as the King James Bible (1611) and Shakespeare, where it pairs with the pronoun "thou" and typically takes the ending -st or -est. Modern readers encountering it should simply read it as "(you) can." Using it today is deliberately quaint or theatrical, appropriate for pastiche, religious quotation, or stylistic effect rather than everyday communication.
Easily confused with canst
"Cant" is a noun meaning hypocritical talk or specialized jargon, whereas "canst" is an archaic verb form of "can"; they differ by only a single letter.
"Cast" means to throw or to shape material, while "canst" is merely an archaic way of saying "you can."