The morning is the part of each day which begins when you get up or when it becomes light outside, and which ends at noon or lunchtime.
the present day
You refer to the morning of the present day as this morning.
His plane left this morning.
‘When did the letter come?’ – ‘This morning.’
You refer to the morning of the previous day as yesterday morning.
They held a meeting yesterday morning.
If something will happen during the morning of the next day, you can say that it will happen tomorrow morning or in the morning.
I've got to go to work tomorrow morning.
Phone him in the morning.
single events in the past
If something happened during a particular morning in the past, use on and mention the particular morning, for example, ‘on Monday morning’.
We left after breakfast on Sunday morning.
On the morning of the exam, she felt sick.
If something happened earlier in the morning during a particular day in the past that you are describing, you can say that it happened that morning or in the morning.
I was late because that morning I had missed my train.
There had already been a meeting in the morning.
If something happened during the morning of the day before a particular day in the past, you can say that it happened the previous morning.
I remembered what she had told me the previous morning.
If something happened during the morning of the day after a day in the past, you say that it happened the next morning, in the morning, next morning, or the following morning.
The next morning I got up early.
In the morning we decided to go out for a walk.
Next morning we drove over to Grandma's.
The ship was due to sail the following morning.
In stories, if you want to say that something happened during a morning in the past, without saying which morning, you say that it happened one morning.
One morning, I was walking to school when I met Dan.
He woke up one morning and found she was gone.
talking about the future
If you want to say that something will happen during a particular morning in the future, you use on and mention the particular morning, for example, ‘on Monday morning’.
They're coming to see me on Friday morning.
He will probably feel very nervous on the morning of the wedding.
If something will happen in the morning during a particular day in the future that you are describing, you can say that it will happen in the morning.
Our plane leaves at 4 pm on Saturday, so we will have time to pack our bags in the morning.
If something will happen during the morning of the day after a particular day in the future, you can say that it will happen the following morning.
I will finish the report on Tuesday evening and send out copies the following morning.
If something happens or happened regularly every morning, you say that it happens or happened in the morning or in the mornings.
Chris usually went swimming in the morning.
The museum is only open in the mornings.
If something happens or happened once a week during a particular morning, you use on followed by the name of a day of the week and mornings.
The post office is closed on Wednesday mornings.
She did her grocery shopping on Saturday mornings.
In American English, you can say that something happens mornings, without ‘on’.
Mornings, she went for a walk if the weather was fine.
You can use in the morning with times of day to make it clear that you are talking about the period between midnight and noon rather than the period between noon and midnight.
They sometimes had meetings at seven in the morning.
We didn't get to bed until four in the morning.*