The article deals with such an interesting and rather complex, multidimensional phenomenon as lacuna on the material of three unrelated languages-Russian, Azerbaijani and English. The lexical lacunae are systematized and analyzed on the following groups: motivated and non-motivated lacunae. Motivated lacuna is connected with the following fact: the native speakers of the other languages do not have this reality idea. Such lacuna can be revealed in the field of the unequal lexeme. However, non-motivated lacuna is not explained by the absence of the idea. The idea exists, but the native speakers of the other languages did not call it owing to the certain cultural, mental, geographical, social, psychological or other reasons. Perhaps, they did not attach importance to them. So, non-motivated lacunae are considered on the concrete lexical-semantic groups in the article :1. Family relationship terms which are divided into two groups: a) blood relations; b) marital relationship. It should be noted that there are no special terms of marital relationship in English unlike Russian and Azerbaijani. The terms of blood relations are used together with the word “law” in postposition in order to denote the necessary marital relationship in English. 2. Nature: natural phenomena, flora and fauna. This group includes a lot of various lacunae connected with nature, natural phenomena. Such lacunae are caused by such objective factors as features of landscape, climatic conditions, relief, predominance of concrete animal, bird, insect, fish species etc. Certainly, the main factor is concrete people’s perception of nature, natural phenomena. Perception of the world influences nomination, highlighting specific natural objects taking into account the degree of their importance. When studying lacunae it is important to take into consideration both extra- and intralinguistic factors.