More on ていく and てくる

Previously I learned about how ていく and てくる are used to indicate the direction of movement with a verb, or indicate a sequence of actions. The following are examples of each:

図書館で本を借りて来る。
I'll go to the library to borrow some books (and will come back).

買い物する前に、銀行でお金をおそして行く。
Before shopping, I'll get some cash from the bank (and then go shopping).

But ていく and てくる can also be used as helper verbs to indicate the temporal direction of something from the speaker's viewpoint. てくる can indicate that an action or process began in the past and is continuing in the present, or that something has begun to take place.

日本語の文法が面白くなってきました。
I'm beginning to find Japanese grammar interesting.
It's gotten to where I find Japanese grammar interesting.

I did two translations there, one from Tobira and one of my own, to give something a bit more literal that pairs with くる's meaning. Thinking of it as "it's gotten to where", "it's come to where", or "it has become" fit well here because they're talking about something that's begun to take place and yet will still continue.

ていく, on the other hand, can be used to indicate that an action or state will continue from the present and into the future.

今学期は一週間に10ずつ新しい漢字を勉強していきます。
This term we are going to study ten new kanji a week.

It's a little harder to offer an alternate translation here, but ていく can often be thought of as "continue" or "to go on [verb]-ing."

最近、ちょっと暖かくなってきました。
Lately it's beginning to get a little warm.

技術が発達したために、生活がとても便利になってきた。
Since technology has developed, life's gotten to where it's really convenient.

この地方は北にあるので、夏は午前4時前に空が明るくなってくる。
Since this area is in the north, in the summer the sky is beginning to get bright before 4 AM.

これから、もっと暖かくなっていきます。
From now on it'll start to get warmer.

ゴールデンレトリバーは大型の犬だから、もっと大きくなっていきますよ。
Since golden retrievers are a large type of dog, they'll continue to get bigger.

ロボットがもっと人々の生活を助けるようになっていくだろう。
Robots will continue to help out more with more with people's daily lives.