Root, third and seventh: the guide tones fix the quality, so the fifth is dropped. That is what leaves a string free, so pick a tension to put on top.
Amaj11 is A, C#, E, G#, B and D — Amaj9 with the eleventh added — the note that fights the major third.
It sounds unsettled, and grittier than the rest of the major family. Most players drop the third or raise the eleventh instead, which is how you arrive at a sus chord or at maj7♯11.
Tonic, awkwardly — the eleventh sits a semitone above the third.

| A | C# | E | G# | B | D |
|---|---|---|---|---|---|
| 1 | 3 | 5 | 7 | 9 | 11 |
Also written AM11, AΔ11 or A major 11. The same chord either way; which spelling you meet depends on who wrote the chart.
Root, third and seventh. The third and seventh, the guide tones, are what make the chord major, minor or dominant, so the fifth can go: it says nothing the symbol needs.
Three notes means a spare string, which is the real point. Put a tension on it.
Amaj11 has 6 of them, on strings 6-4-3-2, the middle four strings, the bottom four strings, the top four strings and strings 5-3-2-1, from the 3rd fret up to the 11th — all in one inversion, so the bass note never moves. The one to learn first is the A shape at the 3rd fret.
Six notes and four fingers, so something has to go. Keep C# and G# (they fix the quality) and D and B (what the symbol is about). Let E and A go, in that order — a perfect fifth says nothing the root has not, and in a band the bass has the root.
Play Amaj11 as a shell — root, third and seventh — and the spare string takes the 13 (F#).
All 9 common shapes as fret numbers, lowest string first. Hover or tap one to see it drawn.
How you get to it. The turn that lands on Amaj11 is Bm7 to E7 — the ii and the V of A — and E7 shares its third and seventh with Bm7, so the hand barely moves between them.
In which keys. Every note of Amaj11 belongs to F# minor (the ♭III) and A major (the I, the tonic).
Every note of Amaj11 is in A major.
Change one note of Amaj11 and you have Amaj9 (drop the eleventh), Amaj13 (the eleventh becomes the thirteenth) or AmMaj11 (the major third becomes the minor third).
Amaj11 is a major chord — root, major third, fifth. Major chords on every root.
The common shapes and the derived voicings come from different places, and both are explained in how this site is built.
Shows each chord the way this style would voice it, and marks which of its alternatives belong to the idiom.