Common chord names

The names in the left hand column are as used in ref 1 and/or 2 as indicated in column 3.   Where one of these references uses a slight variant, that is indicated in column 4.

"sus" is usually a synonym of sus4.    Ref 1 uses "sus".  Ref 2 uses "sus4" Though absent from Ref 1, sus2 chords also exist and are present in Ref 2. Note that Csus2 has the same notes as Gsus4 and the chord will be named according to context.  
Note: the numerals 2 and 4 are conventionally reserved for sus chords, where the 2nd or 4th replaces the 3rd. These intervals are denoted 9 and 11 in other chord names. 

Popularly known as a "half diminished" chord.

9th chords contain a 7th, unless the name is add9: the "add" indicates that there is no 7th.  Ref.2 omits the brackets: Cadd9 instead of C(add9).

In this case there's no ambiguity if the parentheses are omitted.

One or more of the notes shown in parentheses are often omitted from the voicing.

Omitting the 3rd from C11 means that the resullt might sometimes be described as C9sus4.

In maj9 (etc) chords the maj or Δ always define a major 7th. (The 9th is major unless otherwise indicated.)

The Δ notation is particularly useful in this case as it allows the omission of the parentheses.

C6 has the same notes as Am7. This chord will be named according to context.

An exception to the rule that "add" is required to indicate the absence of a 7th!

The 6th in an m6 chord is a major 6th.

Technically a dim7 chord has a minor 3rd and a diminished 5th and 7th, so that Cº7 = CE♭G♭B♭♭. However the use of such chords is usually indicative of a chromatic setting, so that 'simpler' descriptions, such as Cº7 = C E♭ F♯ A have become the norm.

Somtimes Cº or Cdim are used to refer to a diminished triad: Cº=C E♭ G♭, and Cº7, Cdim7 are used to indicate the chord including the diminished 7th.   Reference 2 includes both in this way.   Reference 1 includes only Cº in which it includes the diminished 7th.