Is this normal language behavior?

[GreenGranolaMama]

So I am probably just being paranoid but is it the norm for a toddler (DS is 21 months) to pick up a word or phrase, use it for a few days/ weeks and then stop saying it completely? DS started saying 'I love you' said it almost non stop for a few weeks, but now he won't say it. He's done this with a few other words as well. He is still picking up many new words and still uses many that he has already learned. Just wondering if other little ones do this as well : ) ? 

[sapphire_chan]

Yep. And then eventually the words/phrases come back and are just used normally.