在语法和语义学中，情态指的是一种语言手段，它表明一种观察在多大程度上是可能的、可能的、可能的、确定的、允许的或禁止的。在英语中，这些概念通常（尽管不是唯一）由情态助词表达，如can、may、should和will。它们有时与not结合在一起。

Martin J.Endley认为，“解释情态的最简单方法是说，它与说话人对话语中表达的某种情景所采取的立场有关……[M]情态反映了说话人对所描述情景的态度”（《英语语法的语言学观点》，2010年）。

黛博拉·卡梅隆举例说明：

"[Modality] is what makes the difference between a factual assertion like unicorns never existed, and a more guarded view, such as it seems unlikely that unicorns could ever have existed—or a bolder claim like the existence of unicorns must always have been a myth. Modality, then, is a resource speakers and writers use when they are staking claims to knowledge: it allows them to formulate different kinds of claims (e.g., assertions, opinions, hypotheses, speculations) and indicate how committed they are to those claims." ("The Teacher's Guide to Grammar," Oxford University Press, 2007)

语法上表示情态的

正如时态表示动词的时间方面一样，用来表示情态的词表示句子的语气，即陈述的事实性或断言性，可以通过多种方式完成，包括使用形容词。Martin J.Endley在《英语语法的语言学视角》中解释道：

"Thus, a situation might be described as possible, probable, necessary, or certain. The noun counterparts of these adjectives also express modality so that a situation can be described as a possibility, a probability, a necessity, or a certainty. Moreover, it is possible to use ordinary lexical verbs to convey modality....And think about the difference between saying that you know something and saying that you believe something. Such differences are essentially a matter of modality. Finally, English also contains certain semi-fixed lexical phrases (e.g., rumor has it) that are, basically, modal expressions." (IAP, 2010)

表达情态的其他术语是边缘情态，如需要、应该、敢或习惯。

深入：情态的类型

使用情态表达的可能性范围很广，从不大可能到很可能；为了表达这些不同的层次，情态带有命名的等级，正如作者Günter Radden和RenéDirven在《认知英语语法》中所解释的：

"Modality is concerned with the speaker's assessment of, or attitude towards, the potentiality of a state of affairs. Modality, therefore, relates to different worlds. Assessments of potentiality, as in You must be right, relate to the world of knowledge and reasoning. This type of modality is known as epistemic modality. Modal attitudes apply to the world of things and social interaction. This type of modality is known as root modality. Root modality comprises three subtypes: deontic modality, intrinsic modality and disposition modality. Deontic modality is concerned with the speaker's directive attitude towards an action to be carried out, as in the obligation You must go now. Intrinsic modality is concerned with potentialities arising from intrinsic qualities of a thing or circumstances, as in The meeting can be canceled, i.e. 'it is possible for the meeting to be canceled.' Disposition modality is concerned with a thing's or a person's intrinsic potential of being actualised; in particular abilities. Thus, when you have the ability to play the guitar you will potentially do so....Modal verbs have a special status among modal expressions: they ground a situation in potential reality." (John Benjamins, 2007)