The letter ⟨k⟩ is normally silent (i.e. it does not reflect any sound) when it precedes an ⟨n⟩ at the beginning of a word, as in “knife”, and sometimes by extension in other positions.
Exceptions include the town of Knoebels Grove (/kəˈnoʊbəlz/ kə-NOH-bəlz) located in Pennsylvania in the United States, the Germanic surname Knaus(s) (/kəˈnaʊs/ kə-NOWSS) used by NASCAR crew chief Chad Knaus and First Lady Melania (Knauss) Trump and also words of foreign origin such as Knesset, the name of the Israeli Parliament, etc.
While not as common, the letter ⟨g⟩ is also usually silent (i.e. it does not reflect any sound) when preceding an ⟨n⟩ at the beginning or end of a word, as in “gnat”, “campaign” and “design”.
In addition, the digraph ⟨gh⟩, in the dominant dialects of Modern English, is almost always either silent (as in “bough”, “thorough”, “furlough”, “night” or "weight") or pronounced /f/ (as in “tough”, “enough“ or “laugh”).
In a few words of Greek origin, the digraph ⟨gm⟩ is pronounced /m/, with the (g) being silent, such as in “phlegm”, “paradigm” and "diaphragm".