This is a list of groups.
The letters of each group's name are indicated with underscores(_), words separated by hyphens(-).
As these are groups (containing more than one item), most will end in an s, and this pluralization is given where warranted.
The list of letters that follow the names are the first letter(s) of each member of that group. These letters are not necessarily in traditional order (if such traditional order even exists).
All groups are finite and complete AFAIK unless otherwise noted (‡).
Example:
_ _ _ _ _ - _ _ _ _ _ s
{S, S, T, T S}
Answer: Human - Senses
Group: {Sight, Sound, Taste, Touch, Smell}
1: _ _ _ s
{M, T, T, W, F, S, S}
2: _ _ _ _ _ _ _ _ _ s
{A, A, NA, A, A, SA, E}
3: _ _ _ _ _ - _ _ _ s †
{NA, A, SA, I, NP, SP, A}
4: _ _ _ _ _ _ _ _ _ _ - _ _ _ _ _ _ _ _
{K, P, C, O, F, G, S}
5: _ _ _ _ _ _ - _ _ _ _ _ _ s
{M, B, F, R, A, I}
6: _ _ _ _ _ _ s †
{M, V, E, M, J, S, U, N}
7: _ _ _ _ _ _ _ - _ _ _ _ _ s
{O, G, I, V, R, Y, B}
8: _ _ _ _ _ _ - _ _ _ s
{L, G, G, S, W, E, P}
9: _ _ _ _ _ _ _ _ - _ _ _ _ _ _ s
{C, T, C, D, P, K, H}
10: _ _ _ _ _ s
{J, M, M, J, S, N, F, A, J, A, O, D}
11: _ _ _ _ _ _ _ _ - _ _ _ _ s ‡
{Ra, D, GM, G, MO, f, R, BG, h, JZ}
BONUS: _ _ _ _ _ - _ _ _ _ _ _ _ _ s
{D, C, SS, BT, AC, P, RC, DS, HV, M, PU}
† Modern Definition
‡ Incomplete, only current "Top Ten" shown