The habitual aspect, like the continuous aspect, is also a subclass of the imperfective aspect. It is used when an action occurs repetitively and (usually) predictably. English only has two marked ways of expressing habitual aspect: would + base form of the verb (the infinitive without to) and used to + base form of the verb. When we use these structures, we imply that the action occurred habitually in the past, but does not anymore. For example:
- “When I was young I used to walk to school.”
- “When I was young I would walk to school.”
Although the meaning in the two examples above is the same, used to and would are not always directly interchangeable. For example, used to, standing alone, conveys habitual aspect, but would doesn’t. Observe what happens if we remove the time marker when I was young:
- “I used to walk to school.”
- “I would walk to school.”
When we remove when I was young from the examples, the example using used to retains its habitual aspect, but the example with would doesn’t. Since would can also be used in conditional constructions, we need to include a time marker to clarify when it is being used for the habitual past.
In addition, while used to can be used with both action verbs and stative verbs, would can only be used with action verbs. For example:
- “When I was young, I used to love movies.” (correct)
- “When I was young, I would love movies.” (incorrect)