present participle singing, expressing progressive aspect. It was destroyed. – was is an auxiliary accompanying the past participle destroyed, expressing passive voice. He can do it now. – can is a modal auxiliary accompanying the verb do. However, the above understanding of auxiliaries is not the only one in the literature, particularly in the case of forms of the verb be, which may be called auxiliary even when not accompanying another verb. Other approaches to defining auxiliary verbs are described below. Auxiliaries as verbs with special grammatical behavior A group of English verbs with certain special grammatical (syntactic) properties distinguishes them from other verbs. This group consists mainly of verbs that are auxiliaries in the above sense – verbs that add purely grammatical meaning to other verbs – and thus some authors use the term "auxiliary verb" to denote precisely the verbs in this group. However, not all enumerations of English auxiliary verbs correspond exactly to the group of verbs having these grammatical properties. This group of verbs may also be referred to by other names, such as "special verbs". Non-indicative and non-finite forms of the same verbs (when performing the same functions) are usually described as auxiliaries too, even though all or most of the distinctive syntactical properties do not apply to them specifically: be (as infinitive, imperative and subjunctive), being and been; when used in the expression of perfect aspect, have (as infinitive), having and had (as past participle). Sometimes, non-auxiliary uses of have follow auxiliary syntax, as in Have you any ideas? and I haven't a clue. Other lexical verbs do not do this in modern English, although they did so formerly, and such uses as I know not... can be found in archaic English. Meaning contribution Forms of the verbs have and be, used as auxiliaries with a main verb's past participle and present participle respectively, express perfect aspect and progressive aspect. When forms of be are used with the past participle, they express passive voice. It is possible to combine any two or all three of these uses: The room has been being cleaned for the past three hours. Here the auxiliaries has, been and being (each followed by the appropriate participle type) combine to express perfect and progressive aspect and passive voice. The auxiliary do (does, did) does not typically contribute any meaning (semantic or grammatical), except when used to add emphasis to an