The most influential achievement of corpus linguistics lies in the growing importance of context in the description of language. This is also reflected by context analysis which is introduced in this paper. Context analysis is an umbrella term for a bundle of methods sharing the same hypothesis: that all the features (form, meaning, function) of the language phenomena are mirrored by the context which they enter. It is important to emphasise that by the term ''context'', it is meant here not only one or two adjacent tokens in a particular text, but all the neighbouring units (e.g. words, lemmas, part of speech tags etc.) which co-occur with a given word in all of its instances in a corpus. The paper discusses various types of context (range, type of contextual units etc.) and their effect on the analysis. By comparing contexts of distinct words or word groups we may find out what the similarities and differences are between language units, phenomena or even groups of lexemes. This type of research was conducted here to determine the relations between parts of speech.
Particles as an inflexible and synsemantic word class have already become a theme of many individual studies. According to the general definition particle indicates a relation of the speaker to the statement, he/she expresses modality of the sentence or emphasizes constituent of a/the sentence. Some of the particles have the validity of sentence, e. g. Ano. Nikoli. Zajisté. So called proper particles cannot stand in the function of another word class: ať, kéž. On the contrary, improper particles can be (according with coocurence) another word class, too: jistě, asi, prý. Goal of this paper is to point in which contexts the particle bohužel, although it is a non-sentence expression, can gain the character of sentence equivalent and which functions its synonyms and antonyms have.