There are well-established terms in a language that consist of two or more words. They have a unique meaning that cannot be derived from the meaning of individual words of which they are composed. Units with this status in the lexicon are idioms. Given the frequency of their use, understanding idioms is of great importance for successful communication. The aim of the paper was to examine the ability to understand idioms in adults, since the work of foreign authors about issue does not clearly indicate whether this ability declines with ageing. A total of 57 subjects were divided into two age groups (20 to 25 and 70 to 90 years of age) in which the understanding of the idiom was assessed by defining ten selected terms and describing the situ...