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.