An affricate is a complex consonant that blends a stop (plosive) and a fricative into one sound unit. During production of an affricate, the articulators first form a complete blockage of airflow (as for a stop consonant), then the blockage is released gradually, creating a sustained friction noise (as for a fricative) at the same place of articulation. This coordination makes affricates acoustically and articulatorily distinct from a mere sequence of a stop followed by a fricative. Affricates are found in many languages and pose particular challenges in speech development and disorders, since accurate production requires precise timing between the stop and fricative components.
Peter Roach. English Phonetics and Phonology Glossary. Cambridge University Press, (2009).
Peter Ladefoged and Ian Maddieson. The Sounds of the World’s Languages. Oxford: Blackwell, (1996).