first thing
immediately after you get up, or as soon as you start work

[TahlilGaran] Dictionary of Contemporary English ▲

early arriving or happening before the usual or expected time:
For once, the train arrived early.
Let’s have an early lunch before we go.
in good time especially British English early enough, so that you do not have to rush, or so that you have time to get ready:
Everything was ready for the party in good time.
on time arriving somewhere or happening at the right time:
The bus was on time.
The project was finished on time.
ahead of time earlier than the time when you have arranged to do something or than when you need something:
The building work was completed ahead of time.
Some of the food can be prepared ahead of time.
ahead of schedule earlier than the officially agreed time:
The Prime Minister called the elections early, five months ahead of schedule.
with time to spare arriving somewhere or finishing something before the time when you have to arrive or finish:
We got to the airport with plenty of time to spare.
I finished the test with time to spare.
first thing especially spoken immediately after you get up, or as soon as you start work:
I’ll telephone her first thing tomorrow.
arrive early/be early
Some of the guests arrived early.
leave early
I had to leave early, so I missed the end of the party.
be/get/come home early
Your father said he’d be home early.
get up/wake up/be up early
Set the alarm for six – I have to be up early tomorrow.
go to bed early
I think I’ll go to bed early tonight.
early in the morning/afternoon/evening
We set off early in the morning.
early in May/June etc
I usually go on holiday early in July.
early in 1998/2004 etc
We moved to Manchester early in 2004.
early in the year/century (=in the first part of the year or century)
It was too early in the year for a lot of flowers.

[TahlilGaran] English Thesaurus ▲

first thing
(the) first thing (in the morning)
before doing anything else.
The first thing tomorrow, you'll have to cancel our reservations.

White had a habit of playing his trumpet first thing in the morning, which really irritated his neighbors.

[TahlilGaran] English Idioms Dictionary ▲