きっかけ 'chance', or 切（き）っ掛（か）け in its kanji form is a noun in Japanese that expresses when the trigger of (A) led to (B). It is often translated simply as 'because of (A), (B)', 'with (A) as a trigger, (B)', or 'with the opportunity of (A), (B)'.
きっかけ primarily appears in two different forms. (A)
をきっかけに (B), or (A)
がきっかけで (B). This grammar pattern may be seen either with verbs in their past-tense form or nouns. However, in the case of appearing after verbs, it will often be preceded by の or some other nominalizing structure like こと.
彼女（かのじょ）とは、パーティーで会（あ）ったのをきっかけに付（つ）き合（あ）い始（はじ）めた。
Meeting her at the party led us to start dating.
私（わたし）は入院（にゅういん）をきっかけにタバコを止（や）めることにしました。
Getting hospitalized led me to stop smoking.
この音楽（おんがく）は有名（ゆうめい）な歌手（かしゅ）がカバーしたのがきっかけで再（ふたた）び有名（ゆうめい）になった。
This song became famous again because that famous singer made a cover of it.
このゲームがきっかけで、プログラマーになる事（こと）ができた。
This game led me to become a programmer.
In many cases, the trigger of (A) will have the effect of instigating a rather large change or new beginning.
Caution -
きっかけ will not be used when the causal relationship between (A) and (B) is plainly obvious, due to what would be expected or easy to anticipate result.
木（き）から落（お）ちたのをきっかけに、両腕（りょううで）を骨折（こっせつ）した。
As a result of falling from a tree, I broke both of my arms.
Because of this, it can be thought that
きっかけ is almost always referring to the opportunity of (B) appearing because of (A), with some external choice being made, or action being taken on that occasion.