Guitar & Music Theory Glossary — Every Term in Plain English

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 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 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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.