Auxiliary verb

Auxiliary verbs fall into several classes. The first, and most important, in a pattern that English shares with most European languages, are 'to be' and 'to have'. These are the central auxiliary verbs. Along with 'to do', these three are known as the primary verbs, so important are they.

Their importance can be seen in the role they play in aspect and voice of verb phrases, where they perform multiple functions.

For example, "She was ill the other day" is the simple past of the (semantic) verb 'to be'. In "she was singing", on the other hand, was is an auxiliary which is used to form the continuous past active of the verb 'to sing'. This is 'to be' being used as an auxiliary to form the continuous aspect. In "the referee was kicked by a player", the 'was' shows us a passive 'to be' used to make a past passive tense. These examples show us again that in the study of grammar there are no simple answers that can be learnt by heart. Students have to use their intelligence, judgement and experience to analyse how the words are being used.

In 'The baby was being fed', we have two distinct uses of 'to be'. The was indicates past tense, and the being indicates continuous aspect and passive.

You may also want to see modal verb, primary verb and be.