fill in for
InseparableThe verb and particle never split. The object always follows the whole phrase.
How to say it
Main stress lands on the first particle: fill IN for. The trailing “for” reduces almost to nothing — expect a schwa, not a full vowel.
Link across the gap. The final /l/ of “fill” moves onto the particle and starts its syllable: “fill in” is said “fi-lin”. Pausing between the words is what makes phrasal verbs sound recited rather than spoken.
What it means
To temporarily do someone else's job while they are away.
- “I'm filling in for Dana while she's on leave.”
Similar: cover for, stand in for