# Guitar & Music Theory Glossary — Every Term in Plain English
> A plain-English glossary of guitar and music theory terms — scale, interval, capo, diatonic, voicing and 30+ more, each explained in one or two sentences with guitar examples.
Every guitar tutorial throws around words like "diatonic", "voicing" and "relative
minor" as if everyone went to music school. They didn't. This glossary explains
every term you will meet on this site — in plain English, with a guitar example
for each. Bookmark it; you will be back.

## Accidentals

The sharps (♯) and flats (♭) — notes outside the seven natural letter names. On
guitar, every fret is one semitone, so accidental notes are simply the frets
between the natural notes: the fret between F and G is F♯, also called G♭.

## Arpeggio

A chord played one note at a time instead of strummed together. A C major
arpeggio is the notes C, E and G picked in sequence — the chord, taken apart.

## Barre chord

A chord where one finger (usually the index) presses several strings across the
same fret, so the shape has no open strings and can slide up and down the neck.
F major at the first fret is the classic first barre chord.

## Capo

A clamp that presses all six strings at one fret, acting as a movable nut. A
capo on the 2nd fret turns a C chord shape into a D chord sound — same easy
shapes, higher key. Use the [capo calculator](/tools/capo-calculator) to
transpose in both directions.

## Chromatics

All twelve notes in an octave — the seven naturals plus the five accidentals.
On guitar, playing every fret up one string from open to the 12th fret plays
the chromatic scale.

## Diatonic

Belonging to the key. The seven diatonic chords of C major are C, Dm, Em, F, G,
Am and Bdim — chords built only from the notes of the C major scale. Songs that
"make sense" harmonically are usually fully diatonic. The
[circle of fifths](/tools/circle-of-fifths) shows the diatonic chords of every key.

## Enharmonic

Two names for the same pitch. C♯ and D♭ are the same fret, the same sound —
which name is correct depends on the key you are in. Our chord pages list both
spellings so you can find the page whichever name you searched for.

## Fret

The metal wires across the fingerboard, and by extension the spaces between
them. "Fret the 3rd fret" means press the string down in that space, just
behind the wire.

## Half step (semitone)

The smallest distance in Western music — one fret on the guitar. E to F is a
half step; so is C to C♯.

## Interval

The distance between two notes, measured in semitones or by name (third, fifth,
octave). Chords are defined by their intervals: a major chord is root + major
third (4 semitones) + perfect fifth (7 semitones).

## Inversion

A chord with a note other than the root in the bass. C/E is a C major chord
with E as the lowest note — a first inversion. Inversions make bass lines move
smoothly between chords.

## Key

The tonal centre of a song — the scale and the home chord it revolves around.
A song "in G" uses the G major scale and feels at rest on the G chord. Not sure
what key a song is in? Feed its chords to the [key finder](/tools/key-finder).

## Mode

A scale built by starting the major scale from a different degree. The seven
modes — Ionian, Dorian, Phrygian, Lydian, Mixolydian, Aeolian and Locrian —
share the same seven notes but each has its own mood, because a different note
serves as home.

## Natural notes

The seven notes without sharps or flats: A, B, C, D, E, F, G. On the fretboard
they are the "white keys" of the guitar.

## Nut

The strip of bone or plastic at the top of the neck that the strings cross
before the first fret. In chord diagrams it is the thick line at the top.

## Octave

The same note at double (or half) the frequency. The open low E string and the
2nd fret of the D string are both E, one octave apart — the 12th fret of any
string is exactly one octave above its open note.

## Open chord

A chord that uses one or more open (unfretted) strings. Open chords ring
longer and are easier to finger, which is why beginners start with C, G, D, E
and A. See the [basic guitar chords guide](/guides/basic-guitar-chords).

## Open string

A string played without any finger pressing it — written as "O" above a chord
diagram.

## Power chord

A chord with only the root and fifth — no third, so it is neither major nor
minor. Written as C5 or G5, it is the engine of rock, punk and metal. See the
[power chords guide](/guides/power-chords).

## Progression

The sequence of chords a song moves through, usually described in Roman
numerals relative to the key (I–V–vi–IV). The same numeral pattern works in
every key — try it in the
[chord progression generator](/tools/chord-progression-generator).

## Relative minor

The minor key that shares all seven notes with a major key — A minor is the
relative minor of C major. Every major key has one, three semitones below it,
which is why they share a key signature.

## Root

The note a chord is named after and built from — C is the root of C major.
Usually (but not always) the lowest note; when it isn't, the chord is an
inversion.

## Scale

A set of notes arranged in a fixed step pattern, used as the raw material for
melodies and chords. The major scale's pattern is whole–whole–half–whole–
whole–whole–half. Map any scale across the neck with the
[scale finder](/tools/scale-finder).

## Seventh chord

A triad plus the note a seventh above the root. C7 adds B♭ to C–E–G; Cmaj7
adds B. The small difference between those two notes is the entire difference
between bluesy tension and jazzy smoothness.

## Slash chord

A chord written with a different bass note after a slash: G/B means a G chord
with B as the lowest note. Slash chords make bass lines walk smoothly between
chords.

## Strumming pattern

The repeating rhythm of downstrokes and upstrokes the strumming hand plays —
the groove of a song, independent of its chords. Hear the essential ones in the
[strumming patterns library](/tools/strumming-patterns).

## Diminished chord

A three-note chord built from two stacked minor thirds — a root, a flat third
and a flat fifth. It sounds unstable and usually resolves upwards: the vii° of
any major key is a diminished chord. See
[diminished chord shapes for all 12 roots](/chords/diminished-chords).

## Augmented chord

A three-note chord built from two stacked major thirds — a root, a major third
and a sharp fifth. It sounds unresolved in a floating, cinematic way, and its
shape repeats every four frets. See
[augmented chord shapes for all 12 roots](/chords/augmented-chords).

## Suspended chord (sus2 / sus4)

A chord that replaces the third with the 2nd (sus2) or 4th (sus4) degree, so
it is neither major nor minor — an airy, unresolved sound that usually resolves
back to the plain chord. All twelve roots are collected on the
[suspended chords page](/chords/suspended-chords).

## Tonic

The home note or home chord of a key — the place a song feels finished. In the
key of C, C is the tonic; nearly every song ends on it.

## Transposition

Moving a piece of music to a different key while keeping every interval the
same. Capo on the 2nd fret transposes everything up two semitones without
learning new shapes.

## Triad

A three-note chord: root, third and fifth. Major and minor triads are the atoms
of Western harmony — almost every chord you play is a triad with extra colour
notes added.

## Tuning

The pitches the open strings are set to. Standard tuning is E A D G B E, thick
to thin. Keep yours honest with the
[online guitar tuner](/tools/online-guitar-tuner).

## Voicing

One specific arrangement of a chord's notes on the fretboard. C major has
dozens of voicings from the open position to the 12th fret — same chord,
different flavours. Every chord page on this site shows several.

## Whole step (tone)

Two semitones — two frets on the guitar. Most of the steps in a major scale
are whole steps; the two half steps (between 3–4 and 7–8) are what give the
scale its shape.
## FAQ
### What is the most important music theory term for guitarists?
The interval. Every chord, scale and melody is built from intervals — distances between notes measured in semitones. Once you can hear and name intervals, the rest of theory stops being memorisation and starts being arithmetic.
### Do I need to learn music theory to play guitar?
No — thousands of great players learned by ear. But a small vocabulary (root, fifth, key, capo, diatonic) removes most of the mystery from chord charts and makes learning new songs dramatically faster.
### What is the difference between a chord and a voicing?
A chord is a set of notes (C–E–G is C major); a voicing is one specific way of arranging those notes on the fretboard. The same C major chord has dozens of voicings up the neck.
Canonical page: https://openguitarchords.com/guides/glossary