English verbs are very limited in what they can indicate through their own morphology: using inflexions, they can show past (e.g. cooked) and present tense (e.g. cook), third person agreement (e.g. she cooks), and continuous action (e.g. cooking). Often the main verb needs 'helping out' with a secondary verb form. These are called auxiliary verbs. Auxiliaries are used, for example, to give a sense of time to the main verb (e.g. 'He will be working soon.') or to create a question, 'Have you won?', 'Do you believe it?', 'Could it be true?'. Common auxiliary verbs are forms of to be (is/am/was/are/were/will), to have (has/had/have) and to do (does/did). Some auxiliary verbs are used to remove the sense of action from the main or lexical verb, creating action that exists purely at the level of future potential. These are called modal auxiliaries, e.g. may, might, would, could, should.