The affix mayaṭ comes in the sense of 'product' and 'part' when neither food nor clothing is spoken of, invariably after vṛddha words and śara etc.,
Thus after Vriddha-- आम्रमयम्, शालमयम्, शाकमयम् ॥ After शरादि words:-- शरमयम्,हर्ममयम्, मृन्मयम् ॥
Why do we use the word नित्य 'invariably' in the sutra, when by the mere fact of making a separate sutra, the affix would be obligatory.? The affix मयट्, according to Patanjali comes invariably after words of one syllable. That is done by using the word नित्य in the sutra. Thus, त्वङ् मयम्, स्रङ् मयम्, वाङ् मयम् ॥
1 शर, 2 दर्भ, 3 मृद्, 4 कुटी, 5 तृण, 6 सोम, 7 बल्वज (वल्वज).,