Archaic interjection expressing 'in that way' or 'so'. Not used in modern conversation; appears in classical texts.
In classical Japanese, しか was used as an interjection meaning 'like that' or 'as such'.
Casual interjection of agreement or acknowledgment, similar to 'yeah' or 'uh-huh'. Used in informal speech.
"Wanna go to a movie tomorrow?" "Yeah."
I nod along to my friend's story with an 'uh-huh'.
うん is the common modern casual 'yeah', while 然（しか）is a rarer, old-fashioned-sounding variant with the same agreement function.
however; but
moreover; furthermore; on top of that · nevertheless; and yet; even so
however; nevertheless
proper; appropriate; due; suitable
however; but; and yet
yes; yea; aye; affirmative · to be so
such and such; so-and-so
if so; in that case; then
even so; though that may be
Archaic kanji spelling; the word is now almost always written in kana.
Extremely rare historical kanji; not used in modern writing.
Standard modern kana spelling for both senses.
Derived from classical Japanese 然 (shika), meaning 'in that way'. The casual interjection sense developed from the archaic meaning, but the exact path is uncertain.
therefore; thus; so · well then; by the way
if not so; otherwise
appropriately; properly; as one should
now that; since it is the case that
to put into a state; to bring about a result
if not so; otherwise