If the letter sequence <al> is followed by the consonant letters <f>, <v> or <m>, it is often the case that the <l> is silent and the vowel is pronounced ɑː. Here are some example words:
calf, calves, calve, half, halve, halves, balm, almond, calm, palm, psalm
Exceptions to this where the vowel is æ rather than ɑː ( but the <l> is still silent):
If the letter following the <al> sequence is <k>, again the <l> is silent, but the vowel is pronounced ɔː. Examples:
chalk stalk talk walk
There are also some rather rare words where the spelling is <aul>. For these the <l> is silent and the vowel is ɔː.
baulk, caulk, haulm
Notice that in the word realm where the <a> is part of the sequence <ea> the <l> is NOT silent.
realm = relm