All words can roughly be grouped into three classifications:

Masculine & Feminine

Nouns are classed by whether they are masculine or feminine, and it is the initial letter that determines this.

Masculine nouns begin with:
a, i, u, á, í, ú, â, î, ô, c, ch, d, g, gh, m, mh, n, r

Feminine nouns begin with:
e, o, é, ó, ê, ô, b, bh, f, fh, h, j, jh, l, p, ph, s, sh, t, th

Light (alemgál) & Heavy (tuntgál)

All words are classed as either being “light” or “heavy”, depending on the first letter of the word:

Light words begin with vowels: a, e, i, o, u, á, é, í, ó, ú, â, ê, î, ô

Heavy words begin with consonants: b, bh, c, ch, d, f, fh, g, gh, h, j, jh, l, m, mh, n, p, ph, r, s, sh, t, th

Short (bénagál) & Tall (sàshgál)

All words are classed as either being “tall” or “short”, depending on the last letter of the word:

Short words end with vowels: a, e, i, o, u, á, é, í, ó, ú, â, ê, î, ô

Tall words end with consonants: b, bh, c, ch, d, f, fh, g, gh, h, j, jh, l, m, mh, n, p, ph, r, s, sh, t, th