No tiene nada que ver con prefijos o sufijos. "Blends" es un término propio de método de enseñanza de lectura llamado "Phonics", y se refiere a combinaciones de dos o más consonantes:

"Phonics is a method for teaching reading and writing of the English language by developing learners' phonemic awareness—the ability to hear, identify, and manipulate phonemes—in order to teach the correspondence between these sounds and the spelling patterns (graphemes) that represent them.
The goal of phonics is to enable beginning readers to decode new written words by sounding them out, or in phonics terms, blending the sound-spelling patterns."
http://en.wikipedia.org/wiki/Phonics

"Letter Blends
Certain combinations of two or more consonant letters are called letter blends. Letter blends appear in the beginning or at the end of words to create specific sounds."
Ver la lista en esta fuente
http://www.abcfastphonics.com/letter-blends.html

"Beginning and ending blends"
http://store.ljharper.com.au/stickers-and-stamps/ch6254-begi...