This paper considers the problem of differentiating thought and language in a way that makes it possible to relate them to each other. The analysis covers approaches of sociolinguistic research, different models of language and cognitive functioning within psychology and linguistics, the cybernetic approach, and psycholinguistic analyses. A common approach has been to consider similarities and differences between languages and between cultures in thinking and linguistic forms. More recently, this approach has been extended to include comparisons between subcultures, social classes, and dialects. Another approach has more directly focused on the relation between units of thought and linguistic units. Problems associated with comparisons between languages and cultures and with focusing on linguistic form are discussed. To illustrate the problem of differentiating thought and language, a few examples involving written answers to questions about the meaning of a text are presented. It is concluded that to obtain an understanding of the relation between language and thought, one should study the successive change of conceptions and the use of linguistic forms and the interplay between such changes. Descriptions of the relation between thought and language should be made within a learning or development perspective. A Swedish translation of a portion of the text is appended. (SW)