To Be Mixed
To Be Blended With, To Join
intransitive verb, godan verb
You know that 交ぜる means to mix and that the kanji means mix as well. So, this probably has something to do with mixing things. This word means to be mixed. This is when something is mixed but it's not mixed by you. It's just being mixed. Think of it this way - the じ in 交じる is Jesus, who just uses Jesus magic to mix something. So, you're not mixing it. It's just when something is to be mixed.
まじる
The reading is the same as with 交ぜる. So long as you know the ま portion of that word's reading, you'll be able to read this word as well.
空と海が交じるところが、世かいのはてなのさ。
The place where the sky and the sea meet is the edge of the world.
きたいと不安が交じった気もちです。
My anxiety is mixed with excitement.
わたしのさいふをすった後、そのスリはす早く人ごみに交じってきえました。
After snatching my wallet, the pickpocket quickly blended in with the crowd and disappeared.