This article is an investigation of modality. It considers the term modality to be rather elusive. The present paper aims at contributing to some postulates, pertaining modality, its main properties and ways of expression. It is due to the fact that in linguistics it is possible to find different approaches to the category of modality. It is highlighted that modality is a category of linguistic meaning having to do with the expression of possibility and necessity. As well it is generally accepted that modality should be defined as a semantic domain which covers a range of values (jussive, desirative, eventual, hypothetical, probable, possible, necessary) expressing the opinion, the attitude or the judgment of the utterer in relation to the propositional content of the utterance. In the article the distinction is made between terms modality and mood. It is emphasized that modal expressions can compositionally interact with other expressions. As well in the article five main types of modality, five senses in which the various categories of modality may be understood are distinguished: extensional modality, temporal modality, tense and duration, natural modality, logical and ethical modalities. There is a basic dichotomy in the categorization of modalities, which distinguishes between epistemic and non-epistemic, that is deontic, modality. Its output can be considered in textbooks on theoretical grammar and lexicology, in manuals on modality and the ways of its expression, on the development of English dialogical speech skills.Keywords: modality, expression, mood, epistemology, interaction, negation, probability.