26.02.24: nominative plural of meus, mea, meum and tuus, tua, tuum

26.02.24: nominative plural of meus, mea, meum and tuus, tua, tuum

The possessive adjectives meus, mea, meum and tuus, tua, tuum have endings that look the same as first and second declension nouns:

Masculine: amīcus meus / tuus

Feminine: amīca mea / tua

Neuter: vīnum meum / tuum

Meus, tuus etc. have their own set of endings that happen to be the same as the 1st / 2nd declension nouns and will be used regardless of whether or not the noun is 1st / 2nd declension; an example you saw was nōmen meum / tuum; nōmen (neuter) belongs to a different declension of noun but the possessive adjectives retain the same endings: they do not copy the noun. Similarly [i] liber meus: my book and [ii] you saw the plurals of frāter and soror in the previous post; they are not second declension nouns but the possessive adjectives still retain the same endings.

frāter meus / tuus: my / your brother

frātrēs meī / tuī: my / your brothers

soror mea / tua: my / your sister

sorōrēs meae / tuae: my / your sisters

That the endings are identical applies to all forms of these words i.e. the same as the 1st / 2nd declension nouns:

Nominative Singular

Masculine: amīcus meus; stilus tuus

Feminine: amīca mea; tabula tua

Neuter: pōculum meum; scūtum tuum

Nominative Plural

Masculine: amīcī meī; stilī tuī

Feminine: amīcae meae; tabulae tuae

Neuter: pōcula mea; scūta tua

Spend some time looking at the example structures in the image posted.