The natural-language basis of scientific languages is noted in a discussion of the conventionality of language as a semantic system. Semantic convention and metaphor are analyzed from a gnoseological perspective, and the iconicity and polysemy of the latter are characterized. It is observed that both semantic convention and metaphor are important means of expanding a scientific language's vocabulary, although each does it through a different mode of reference to the denotat. It is noted that metaphor appeals to the imagery and feeling, whereas convention - in both its trivial (semantic convention) and elaborated forms (empirical and theoretical conventions) - allows an explicit formulation of new knowledge and relates the emotional and rational in scientific inquiry. The metaphorical and conventional nature of scientific terms is most explicit in (1) the communication between scientists, (2) the training of scientists, (3) research in new scientific fields, and (4) new scientific theories. (Copyright 1992, Sociological Abstracts, Inc., all rights reserved.) (Z. Dubiel in LLBA 1992, vol. 26, n. 3)