This chapter gives an introductory overview of the basic typological properties of the languages of mainland Southeast Asia, including the morphological profile, and the relative position of major components of phrases, including clauses, noun phrases, adpositional phrases, and comparative constructions. The chapter discusses sentence type distinctions, with a special focus on sentence-final particles, which are found across the mainland Southeast Asia area. The chapter features a section on expressive language, including expressives/ideophones and poetic idioms.