The letters я and ю never occur after noisy consonants (ч щ ш ж ц) and velars (к г х). That is why the 3rd Plural of some 2nd conjugation verbs is -ат rather than -ят, e.g. полћжат 'they will put' (vs. говорїт 'they speak'). That is also why the 1st Singular of some 2nd conjugation verbs is -у instead of -ю, e.g. вќдят 'they see', but вќжу 'I see' (vs. говорє 'I speak').