If / even if
The four 'if' endings plus 'even if', all on one 'jikan aru' sentence so only the ending changes.
-tara
if; when; once
たら
Conditional built on the -ta form: 'if' for hypotheticals, 'when / once' for things sure to happen, and 'when I did X, I found Y' in stories. The safe default when unsure which 'if' fits.
jikan attara, kite ne.
If you've got time, come by.
時間あったら、来てね。
jikan ga attara, kite kudasai ne.
If you have time, please come by.
時間があったら、来てくださいね。
Polite speech keeps plain -tara; -mashitara sounds very formal.
-nara
if (that's the case); as for
なら
Takes up something just said or known and builds on it: 'if it's X / if you're going to X'. Attaches to nouns and plain forms ('sushi nara, ii mise shitteru').
jikan aru nara, tetsudatte yo.
If you've got time, help me out.
時間あるなら、手伝ってよ。
jikan ga aru nara, chotto tetsudatte moraemasu ka?
If you've got time, could you give me a hand?
時間があるなら、ちょっと手伝ってもらえますか？
English speakers overuse nara for every 'if'; save it for picking up what was said. Timing trap: with nara the main action can come first ('nihon ni iku nara, kore yonde' = read this before you go), while 'nihon ni ittara, ...' = once you're there.
-te mo
even if; even though
ても
Te-form + mo: the result holds anyway ('ame ga futte mo iku'). Adjectives take -kute mo, nouns and na-adjectives de mo; casual alternative -tatte.
jikan atte mo, ikanai.
Even if I have time, I'm not going.
時間あっても、行かない。
jikan ga atte mo, ikimasen.
Even if I have time, I won't go.
時間があっても、行きません。
Listen for what follows: 'tabete mo ii?' = 'can I eat it?', while 'tabete mo, ...' = 'even if I eat'. Don't treat -te mo as a kind of -tara; it flips the meaning ('even if' vs 'if').
-ba
if
ば
Conditional on the e-stem (areba, ikeba, yasukereba): 'if X, then Y', often with the sense that X is all it takes. Also inside -ba ii, -nakereba and dou sureba.
jikan areba, iku yo.
If I have time, I'll go.
時間あれば、行くよ。
jikan ga areba, ikimasu.
If I have time, I'll go.
時間があれば、行きます。
Casually -nakereba shrinks to -nakya; -kerya / -rya (yokerya, arya) sound rough and male: recognise, don't produce. After an action verb, -ba can't lead into a request or invitation; use -tara ('tsuitara, denwa shite').
Learn alongside: -tara, -nara, -te mo, -toLearn first: -tara
-to
whenever; if (then always)
と
Plain form + to: Y always or automatically follows X; used for directions, how things work and habits ('migi ni magaru to, eki ga aru'). The main clause can't be a request, invitation or plan.
jikan aru to, itsumo nechau.
Whenever I have time, I end up sleeping.
時間あると、いつも寝ちゃう。
jikan ga aru to, itsumo nechaimasu.
Whenever I have time, I end up sleeping.
時間があると、いつも寝ちゃいます。
'...to, kite' (a request) is wrong; use -tara for that.
Learn alongside: -tara, -nara, -te mo, -baLearn first: -tara