Using と to Express "If" or "Whenever"

Did I mention before that there are at least four ways to express "if" in Japanese? It's great. Well, here's another one, although based on the examples given in Genki, it can read more like "whenever." I'll use that in my examples since that makes it easier to differentiate from other "if" words.

A short form predicate + と means that whenever the aforementioned situation occurs, another thing happens. For example, "Whenever I open the cabinet, my cat gets excited for food." In most cases, と sentences describe a cause/effect type scenario.

Clause A と Clause B - Whenever A happens, B happens too.

The first clause in the sentence must be in present tense, while the second can be in past or present tense.

アヤトに会うとうれしくなる。
Whenever I see Ayato, I feel happy.

私はりんごを食べると友達はバナナを食べる。
Whenever I eat an apple, my friend eats a banana.

私たちは合格すると市内の店でお菓子をたくさん買うよ。
Whenever we pass a test, we buy a bunch of candy from the local shop.

Note that the event in the second clause must follow the first one. It would not make sense to use と here to express something in the second clause that happens before the first.

Also note that if an adjective is used in the second half of the sentence, rather than a verb, it's usually expressed as a change, often with なる.

ロマンチックな映画を見ると悲しくなるよ。
Whenever I watch a romantic movie, I get sad.

ロックを聞くと元気になる。
Whenever I hear rock music, I feel uplifted.