The best way to learn proper English is to read news report, and watch news on TV. Watching TV shows is a great way to learn casual English, slang words, understand culture reference and humor. If you have already watched these shows then you may recall the words used in the following dialogs.

I can't believe you have to fill out
a preschool application for an INFANT.
The Big Bang Theory Season 10, Episode 15

He didn't decide to kill her.
He was an INFANT.
Game of Thrones Season 4, Episode 10

for new parents
to take an INFANT CPR class.
The Big Bang Theory Season 10, Episode 10

Oh, God, we are not ready to have
an INFANT in this house.
The Big Bang Theory Season 10, Episode 6

who had traded his INFANT son for a dog.
Game of Thrones Season 5, Episode 2