accompanying verb. This is called the emphatic mood in English: An example would be "I do go to work on time every day" (with intonational stress placed on do), compared to "I go to work on time every day." As an auxiliary, do mainly helps form questions, negations, etc., as described in the article on do-support. Other auxiliaries – the modal verbs – contribute meaning chiefly in the form of modality, although some of them (particularly will and sometimes shall) express future time reference. Their uses are detailed at English modal verbs, and tables summarizing their principal meaning contributions can be found in the articles Modal verb and Auxiliary verb. For more details on the uses of auxiliaries to express aspect, mood and time reference, see English clause syntax. Contracted forms Contractions are a common feature of English, used frequently in ordinary speech. In written English, contractions are used in mostly informal writing and sometimes in formal writing. They usually involve the elision of a vowel – an apostrophe being inserted in its place in written English – possibly accompanied by other changes. Many of these contractions involve auxiliary verbs and their negations, although not all of these have common contractions, and there are also certain other contractions not involving these verbs. Contractions were first used in speech during the early 17th century and in writing during the mid 17th century when not lost its stress and tone and formed the contraction -n't. Around the same time, contracted auxiliaries were first used. When it was first used, it was limited in writing to only fiction and drama. In the 19th and 20th centuries, the use of contractions in writing spread outside of fiction such as personal letters, journalism, and descriptive texts. Certain contractions tend to be restricted to less formal speech and very informal writing, such as John'd or Mary'd for "John/Mary would" (compare the personal pronoun forms I'd and you'd, which are much more likely to be encountered in relatively informal writing). This applies in particular to constructions involving consecutive contractions, such as wouldn't've for "would not have". Contractions in English are generally not mandatory as in some other languages. It is almost always acceptable to use the uncontracted form, although in speech this may seem overly formal. This is often done for emphasis: I am ready! The uncontracted form of an auxiliary or copula must be used in