Past tense

The main rule is that for every verb in English, there is only one form of it in the past tense. 
(The exception is the Past tense of To Be, which has two forms: was and were).

To change a regular verb into its past tense form, we normally add –ED to the end of the verb.

• play – played
• cook – cooked
• rain – rained
• wait – waited

Irregular verbs are ONLY irregular in affirmative/positive sentences.

For example: The past tense of GO is WENT.
It does not end in –ED so it is considered irregular.