The Perfect Day

day off

if I have a day off, I would probably sleep.

A day off is day you do not have school or work. Notice the following:

1. I go to the beach on my day off.
   
2. On my day off, I do nothing!

sleep in

I would probably sleep in.

When you sleep in, you do not get up early. You stay in bed longer than usual. Notice the following:

1. I don't work Fridays, so I can sleep in that day.
   
2. I like to get up early, so I never sleep in.

certainly

I certainly would swim in the sea

The adverb certainly shows that something is true or likely.

1. I would certainly move overseas if i had the chance.
   
2. He certainly was not happy! He looked so mad.

especially

I love swimming, especially in the sea.

The adverb especially shows that something is emphasised more than other things.

1. I love old movies, especially old crime dramas.
   
2. The city has lots of good restaurants, especially by the river.

sounds like

That sounds like an ideal summer day to me

Here, the verb 'sound' is a stative verb like the following: look, smell, appear, sound, and feel. The meaning is very similar to the verb 'be' and shows what a person thinks.

1. That sounds like a good idea.
   
2. That sounds like fun!