Use the noun notation to describe a written note, like the comments an English teacher makes in the margins of a student's essay.
An editor might make notations on an article, and a conductor might add notations — written reminders to herself — to the edges of a musical score. Another kind of notation is a series of symbols that represent words, numbers, or music, for example. Chemical formulas are one type of notation, and musical notes are another. Notation comes from the Latin word notationem, which means "a marking or an explanation," from the root nota, "mark."
Primary Meanings of notation
1. 
n 
a comment or instruction (usually added)

2. 
n 
a technical system of symbols used to represent special things

Full Definitions of notation
1
n a comment or instruction (usually added)
“he added a short
notation to the address on the envelope”
 Synonyms:
 annotation, note
 Types:
 show 7 types...
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poste restante
a notation written on mail that is to be held at the post office until called for (not in the United States or Canada)

acknowledgment, citation, cite, credit, mention, quotation, reference
a short note recognizing a source of information or of a quoted passage

footer, footnote
a printed note placed below the text on a printed page

N.B., NB, nota bene
a Latin phrase (or its abbreviation) used to indicate that special attention should be paid to something

PS, postscript
a note appended to a letter after the signature

photo credit
a note acknowledging the source of a published photograph

crossindex, crossreference
a reference at one place in a work to information at another place in the same work
 Type of:

comment, commentary
a written explanation or criticism or illustration that is added to a book or other textual material
2
n a technical system of symbols used to represent special things
 Synonyms:
 notational system
 Types:
 show 40 types...
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mathematical notation
a notation used by mathematicians

musical notation
(music) notation used by musicians

choreography
a notation used by choreographers

chemical notation
a notation used by chemists to express technical facts in chemistry

bar line
a vertical line before the accented beat marking the boundary between musical bars

number representation system, number system, numeration system, system of numeration
any notation for the representation of numbers

binary notation
any notation that uses 2 characters (usually 0 and 1)

decimal notation
any notation that uses 10 different characters (usually the digits 0 to 9)

octal notation
any mathematical notation that uses 8 different characters (usually the digits 0 to 7)

duodecimal notation
any notation that uses 12 different characters

hexadecimal notation, sexadecimal notation
any notation that uses 16 different characters

sign
a character indicating a relation between quantities

decimal point, percentage point, point
the dot at the left of a decimal fraction

exponent, index, power
a mathematical notation indicating the number of times a quantity is multiplied by itself

fixedpoint notation, fixedpoint representation system
a radix numeration system in which the location of the decimal point is fixed by convention

floatingpoint notation, floatingpoint representation system
a radix numeration system in which the location of the decimal point is indicated by an exponent of the radix; in the floatingpoint representation system, 0.0012 is represented as 0.122 where 2 is the exponent

infix notation
a notation for forming mathematical expressions using parentheses and governed by rules of operator precedence; operators are dispersed among the operands

parenthesisfree notation
a notation for forming mathematical expressions that does not use parentheses to delimit components

tablature
a musical notation indicating the fingering to be used

Labanotation
a system of notation for dance movements that uses symbols to represent points on a dancer's body and the direction of the dancer's movement and the tempo and the dynamics

musical scale, scale
(music) a series of notes differing in pitch according to a specific scheme (usually within an octave)

interval, musical interval
the difference in pitch between two notes

staff, stave
(music) the system of five horizontal lines on which the musical notes are written

clef
a musical notation written on a staff indicating the pitch of the notes following it

key signature, signature
the sharps or flats that follow the clef and indicate the key

key, tonality
any of 24 major or minor diatonic scales that provide the tonal framework for a piece of music

atonalism, atonality
the absence of a key; alternative to the diatonic system

musical time signature, time signature
a musical notation indicating the number of beats to a measure and kind of note that takes a beat

bar, measure
musical notation for a repeating pattern of musical beats

rest
a musical notation indicating a silence of a specified duration

musical note, note, tone
a notation representing the pitch and duration of a musical sound

slur
(music) a curved line spanning notes that are to be played legato

sharp
a musical notation indicating one half step higher than the note named

flat
a musical notation indicating one half step lower than the note named

cancel, natural
a notation cancelling a previous sharp or flat

accidental
a musical notation that makes a note sharp or flat or natural although that is not part of the key signature

fermata
a musical notation (over a note or chord or rest) that indicates it is to be prolonged by an unspecified amount

solmisation, solmization
a system of naming the notes of a musical scale by syllables instead of letters

segno
(music) a notation written at the beginning or end of a passage that is to be repeated

sforzando
(music) a notation written above a note and indicating that it is to be played with a strong initial attack
 Type of:

writing
letters or symbols that are written or imprinted on a surface to represent the sounds or words of a language
n the activity of representing something by a special system of marks or characters
 Type of:

committal to writing, writing
the activity of putting something in written form