THE THIRD PERSON SINGULAR of the simple present.
The basic rule is that you add “-s” to the infinitive form.

1. to run – he runs
2. to eat – she eats
3. to rain – it rains

After certain infinitive endings you must add “-es.”

1. to go – he goes
2. to kiss – he kisses
3. to push – he pushes
4. to touch – he touches
5. to box – he boxes
6. to buzz – it buzzes

If you have a consonant plus “y,” the third person ending is “-ies.”

1. to try – she tries
2. to fly – it flies

Note that this is not the case if the “y” is preceded by a vowel.

1. to play – he plays
2. to stay – she stays

Remember that the modal auxiliaries have no “s” in the third person singular.

1. can – he can
2. may – she may
3. must – it must

THE SIMPLE PAST AND THE PAST PARTICIPLE.
The general rule is to add “-ed” to the infinitive.

1. to work – I worked – you have worked
2. to pass – she passed – they have passed
3. to land – we landed – they have landed

After “e” just add “-d.”

1. to reduce – they (have) reduced
2. to receive – we (have) received

A consonant plus “y” becomes “-ied.”

1. to cry – she (has) cried
2. to try – I (have) tried
3. to reply – you (have) replied

Note that, as before, a “y” preceded by a vowel is not modified.

1. to stay – you (have) stayed
2. to display – they (have) displayed

After a simple, accentuated vowel followed by a single consonant, the consonant is doubled before we add “-ed.”

1. to stop – they (have) stopped

THE PRESENT PARTICIPLE.
The basic rule is to add “-ing” to the infinitive.

1. to work – working
2. to stand – standing
3. to play – playing
4. to try – trying

If the infinitive ends in a consonant plus “e,” we normally drop the “e” before adding “-ing.”

1. to smile – smiling
2. to hope – hoping

But don’t forget the following cases.

1. to be – being
2. to die – dying
3. to lie – lying
4. to see – seeing

As before, the consonant is doubled after a simple, accentuated vowel followed by a single consonant:

• to stop – stopping