A consonant digraph is a combination of two consonant letters that form a single consonant sound. The common English consonant digraphs are CH, DG, DJ, GH, NG, PH, SH, SS, TH, and WH. Each digraph can represent different speech sounds depending on factors like the surrounding letters and position in a word. For example, CH can represent /ʧ/, /k/, or /ʃ/; GH can represent /g/, /f/, or be silent; NG usually represents /ŋ/ but can also represent /ng/ or /nʤ/ between syllables. Understanding the various sounds each digraph can make is important for reading and spelling English words correctly.