This research compares the use of triadic dialogue and translanguaging in two multilingual grade seven classrooms where algebra is taught in a foreign language. Ten lessons in one classroom that involve teaching properties and seven lessons in another classroom that involve teaching conventions were video- and audio-recoded and then transcribed. Teacher and learners' utterances were coded at different levels: school, session, interlocutor, language use, and move and function. Quantitative analyses and qualitative illustrations of interaction, discourse, and translanguaging are reported and analyzed. The triadic dialogue (initiation-response-follow-up) turn-taking structure is the dominant style of classroom interaction. Dominant functions of the triadic dialogue and translanguaging in each classroom are identified and analyzed. The findings are discussed from a socio-cultural perspective in which language is viewed as a medium for the process of teaching and learning.