Base verb (say, tell) or ending in ‘s’ in the third person singular
The present simple is used to talk about something that is factual and true in the present moment.
He is twenty-five years old.
They are very excited about the journey this afternoon.
Anne is an engineer.
We use the present simple to talk about something that is fixed for the future, especially when that something has a fixed date like an expression of time.
Our college semester begins next week.
She catches the train at the station at 21h.
We are both going to Australia on Friday.
We use the present simple to talk about facts. Any factual piece of information.
Water boils at one-hundred degrees Celsius.
A match burns when being lighted.
The human mind is a very complex system.
I seldom go to music class on Tuesday evenings.
She sometimes likes to dance the tango at the weekend.
I rarely play chess during the week.
Sally sometimes goes to her art’s class.
They never show up for class.
Remember that the adverb always goes after the subject and before the verb. But only with ordinary verbs and NOT with auxiliary verbs.
With an ordinary verb:
1) I sleep sometimes on the sofa. ✗ 2) I sometimes sleep on the sofa. ✓
With an auxiliary verb:
1)I always am here. ✗
2) I am always here. ✓
We use -do/does -don’t/doesn’t to form questions, negate answers and questions (where what and why) and to apply emphasis (negative or positive) in the present tense.
Where do you live? I live in Britain.
What does she do for a living? She is a teacher.
Why do they behave so strangely? I wouldn’t have a clue.
I don’t live in Paris, France.
She doesn’t like sweet food.
We use the auxiliary verb -do to emphasise in English. Emphasis in full detail
Do you go to work on Mondays? Yes, I do go to work on Mondays. (It is assumed that the recipient wants to emphasise the fact that he/she works on Mondays).
She does play volleyball every weeknight. (It is emphasised that she does indeed play volleyball every weeknight).
I do not have a problem with them. (to negate in the negative, we avoid using the contraction altogether for emphasis).
He does not study enough. (Here, there is more emphasis than say, ‘he doesn’t study enough.’