外が明るくなってきた。

outside; exterior; open air; other place

indicates sentence subject (occasionally object); indicates possessive (esp. in literary expressions); but; however; still; and

bright; colourful; cheerful; familiar (with); knowledgeable (about); fair (e.g. politics); clean

to become; to get; to grow; to be; to reach; to attain; to result in; to prove to be; to consist of; to be composed of; to succeed; to be complete; to change into; to be exchanged for; to play a role; to be promoted; to do ...