Copy ṁ, the m with a dot above, or ẋ, Q̇ and V̇: dotted letters that stand for a rate.
M Dot Symbol
ṁLatin small letter m with dot aboveU+1E41Ready to copy
44 letters with a dot above. Tap any value to copy it.
44 letters with a dot above. A character and its name both copy the character. A code copies the code.
Character
Name
Code point
Alt code
Option keys
HTML
U+1E41. m dot as one character: the usual symbol for mass flow rate, the mass of a fluid passing per unit of time. \dot{m} in LaTeX maths. In neither Alt code table.
U+1E40. The capital letter, one character as well. \dot{M} in LaTeX maths.
U+1E8B. x dot as one character. With x a position, ẋ is its velocity: the rate at which x changes with time.
U+1E8D. x double dot as one character; Unicode names the two dots a diaeresis. With x a position it is the acceleration. \ddot{x} in LaTeX maths.
Made of U+0051 and U+0307. Heat transfer rate: the heat flowing per unit of time. Unicode has no single character for it, so it is two code points.
Made of U+0056 and U+0307. Volume flow rate, which is more often written as a plain Q.
U+1E8F. y dot as one character: the rate at which y changes with time.
U+0307. The dot itself. Unicode's note: derivative (Newtonian notation). Typed straight after a letter it sits over that letter. No named entity; ̇ in a web page.
U+1E8A. The capital of ẋ, one character as well.
U+0116. Capital E dot as one character. With ṁ it gives an energy flow rate: Ė = ṁe, the mass flow rate times the energy per unit of mass. Ė in HTML.
U+1E86. Capital W dot as one character.
U+0227. a dot as one character. Unicode's note: Uralicist usage.
U+1E03. b dot as one character. Unicode's note: Irish Gaelic (old orthography).
U+010B. c dot as one character. Unicode's note: Maltese, Irish Gaelic (old orthography). ċ in HTML.
U+1E0B. d dot as one character. Unicode's note: Irish Gaelic (old orthography).
U+0117. e dot as one character. Unicode's note: Lithuanian. ė in HTML.
U+1E1F. f dot as one character. Unicode's note: Irish Gaelic (old orthography).
U+0121. g dot as one character. Unicode's note: Maltese, Irish Gaelic (old orthography). ġ in HTML.
U+1E23. h dot as one character.
U+1E45. n dot as one character. Unicode's note: Indic transliteration.
U+022F. o dot as one character.
U+1E57. p dot as one character. Unicode's note: Irish Gaelic (old orthography).
U+1E59. r dot as one character.
U+1E61. s dot as one character. Unicode's note: Irish Gaelic (old orthography).
U+1E6B. t dot as one character. Unicode's note: Irish Gaelic (old orthography).
U+1E87. w dot as one character.
U+017C. z dot as one character. ż in HTML.
Made of U+0071 and U+0307. The small letter q has no ready-made form either.
Made of U+03B8 and U+0307. With θ an angle, this is the angular velocity, also written ω.
Made of U+03C9 and U+0307. Angular acceleration: the rate at which the angular velocity ω changes with time.
Made of U+0075 and U+0307. The letter u with the combining dot.
Made of U+0076 and U+0307. The letter v with the combining dot.
U+1E8C. The capital of x double dot, one character as well.
U+00FF. y double dot as one character, and the only letter here with an Alt code: Alt+152 or Alt+0255. ÿ in HTML.
Made of U+0072 and U+0308. The letter r with the combining diaeresis: two dots.
Made of U+03B8 and U+0308. Two dots over θ: its second derivative with respect to time.
Made of U+0078 and U+20DB, combining three dots above: the third derivative. With x a position it is the jerk, the rate at which acceleration changes. A device with no font for the mark draws an empty box.
Made of U+0078 and U+20DC, combining four dots above: the fourth derivative. A device with no font for the mark draws an empty box.
U+0308. Two dots, which Unicode also calls double dot above and double derivative. ̈ in a web page.
U+20DB. Unicode's note: third derivative. ⃛ in HTML.
U+20DC. Unicode's note: fourth derivative. ⃜ in HTML.
U+02D9. A dot that takes its own space and covers nothing: it does not move over the letter before it. Option+H, or ˙ in HTML.
U+1E43. Not this sign: the dot sits under the letter. Unicode's note: Indic transliteration.
Made of 0, a decimal point, 3 and U+0307. Not a rate: a dot over a digit marks a decimal that repeats without end.
The m dot symbol is ṁ: an m with a dot above, one character, U+1E41. In physics and engineering it is the usual sign for mass flow rate. The x dot symbol, ẋ, is one character too; Q̇ has to be built.
Read the full guide
What the dot says
A dot over a letter is the rate at which that quantity changes with time. ṁ is mass flow rate, V̇ volume flow rate and Q̇ heat transfer rate. With x a position, ẋ is velocity and x with two dots is acceleration. Three dots make it jerk.
How to type a dot above a letter
Type the letter, then U+0307, Combining dot above, straight after it: the mark sits over the letter before it. In a web page that is ṁ, and in LaTeX maths \dot{m}, or \ddot{x} for two dots. With a Compose key, ṁ is Compose, period, m.
Nineteen small letters have a ready-made form with a dot above. k, l, q, u and v have none, so they take U+0307.
In Irish set in the old Gaelic type, ṁ is a lenited m, the sound spelled mh in Roman type.
A dot over a digit is another sign: over the 3 of 0.3 it marks a repeating decimal.
Questions and answers
What is the Alt code for m dot?
ṁ is in neither Alt code table, so no standard Alt code types it. Some apps, rich text editors in particular, read a code above 255 as a Unicode code point, and there Alt+7745 gives ṁ.
What does the m dot symbol mean?
Mass flow rate: the mass of a fluid that passes through a surface per unit of time, in kilograms per second. It is said m-dot, and the dot is Newton’s way of writing a rate of change with time.
Is m with a dot above one character?
Yes. ṁ is U+1E41 and the capital Ṁ is U+1E40; each equals the plain letter followed by U+0307. Q̇ and V̇ have no ready-made form, so they are always two code points.
What is the x double dot symbol?
It is U+1E8D, one character, which Unicode names x with diaeresis. Two dots are the second derivative with respect to time: if x is a position, that is its acceleration. The single-dot ẋ is U+1E8B.
All 44 letters with a dot above
Start here 8
Q̇Capital Q dotMade of U+0051 and U+0307. Heat transfer rate: the heat flowing per unit of time. Unicode has no single character for it, so it is two code points.
V̇Capital V dotMade of U+0056 and U+0307. Volume flow rate, which is more often written as a plain Q.
̇Combining dot aboveU+0307. The dot itself. Unicode's note: derivative (Newtonian notation). Typed straight after a letter it sits over that letter. No named entity; ̇ in a web page.
ṀLatin capital letter m with dot aboveU+1E40. The capital letter, one character as well. \dot{M} in LaTeX maths.
ṁLatin small letter m with dot aboveU+1E41. m dot as one character: the usual symbol for mass flow rate, the mass of a fluid passing per unit of time. \dot{m} in LaTeX maths. In neither Alt code table.
ẍLatin small letter x with diaeresisU+1E8D. x double dot as one character; Unicode names the two dots a diaeresis. With x a position it is the acceleration. \ddot{x} in LaTeX maths.
ẋLatin small letter x with dot aboveU+1E8B. x dot as one character. With x a position, ẋ is its velocity: the rate at which x changes with time.
ẏLatin small letter y with dot aboveU+1E8F. y dot as one character: the rate at which y changes with time.
Show all 44 letters with a dot above (36 more)
One character 19
ĖLatin capital letter e with dot aboveU+0116. Capital E dot as one character. With ṁ it gives an energy flow rate: Ė = ṁe, the mass flow rate times the energy per unit of mass. Ė in HTML.
ẆLatin capital letter w with dot aboveU+1E86. Capital W dot as one character.
ẊLatin capital letter x with dot aboveU+1E8A. The capital of ẋ, one character as well.
ȧLatin small letter a with dot aboveU+0227. a dot as one character. Unicode's note: Uralicist usage.
ḃLatin small letter b with dot aboveU+1E03. b dot as one character. Unicode's note: Irish Gaelic (old orthography).
ċLatin small letter c with dot aboveU+010B. c dot as one character. Unicode's note: Maltese, Irish Gaelic (old orthography). ċ in HTML.
ḋLatin small letter d with dot aboveU+1E0B. d dot as one character. Unicode's note: Irish Gaelic (old orthography).
ėLatin small letter e with dot aboveU+0117. e dot as one character. Unicode's note: Lithuanian. ė in HTML.
ḟLatin small letter f with dot aboveU+1E1F. f dot as one character. Unicode's note: Irish Gaelic (old orthography).
ġLatin small letter g with dot aboveU+0121. g dot as one character. Unicode's note: Maltese, Irish Gaelic (old orthography). ġ in HTML.
ḣLatin small letter h with dot aboveU+1E23. h dot as one character.
ṅLatin small letter n with dot aboveU+1E45. n dot as one character. Unicode's note: Indic transliteration.
ȯLatin small letter o with dot aboveU+022F. o dot as one character.
ṗLatin small letter p with dot aboveU+1E57. p dot as one character. Unicode's note: Irish Gaelic (old orthography).
ṙLatin small letter r with dot aboveU+1E59. r dot as one character.
ṡLatin small letter s with dot aboveU+1E61. s dot as one character. Unicode's note: Irish Gaelic (old orthography).
ṫLatin small letter t with dot aboveU+1E6B. t dot as one character. Unicode's note: Irish Gaelic (old orthography).
ẇLatin small letter w with dot aboveU+1E87. w dot as one character.
żLatin small letter z with dot aboveU+017C. z dot as one character. ż in HTML.
Letter and dot 5
ω̇Omega dotMade of U+03C9 and U+0307. Angular acceleration: the rate at which the angular velocity ω changes with time.
q̇Small q dotMade of U+0071 and U+0307. The small letter q has no ready-made form either.
θ̇Theta dotMade of U+03B8 and U+0307. With θ an angle, this is the angular velocity, also written ω.
u̇u dotMade of U+0075 and U+0307. The letter u with the combining dot.
v̇v dotMade of U+0076 and U+0307. The letter v with the combining dot.
Two dots and more 6
ẌLatin capital letter x with diaeresisU+1E8C. The capital of x double dot, one character as well.
ÿLatin small letter y with diaeresisU+00FF. y double dot as one character, and the only letter here with an Alt code: Alt+152 or Alt+0255. ÿ in HTML.
r̈r double dotMade of U+0072 and U+0308. The letter r with the combining diaeresis: two dots.
θ̈Theta double dotMade of U+03B8 and U+0308. Two dots over θ: its second derivative with respect to time.
x⃜x four dotsMade of U+0078 and U+20DC, combining four dots above: the fourth derivative. A device with no font for the mark draws an empty box.
x⃛x triple dotMade of U+0078 and U+20DB, combining three dots above: the third derivative. With x a position it is the jerk, the rate at which acceleration changes. A device with no font for the mark draws an empty box.
The marks alone 4
̈Combining diaeresisU+0308. Two dots, which Unicode also calls double dot above and double derivative. ̈ in a web page.
⃜Combining four dots aboveU+20DC. Unicode's note: fourth derivative. ⃜ in HTML.
⃛Combining three dots aboveU+20DB. Unicode's note: third derivative. ⃛ in HTML.
˙Dot aboveU+02D9. A dot that takes its own space and covers nothing: it does not move over the letter before it. Option+H, or ˙ in HTML.
Not a dot above 2
ṃLatin small letter m with dot belowU+1E43. Not this sign: the dot sits under the letter. Unicode's note: Indic transliteration.
0.3̇One third with a dot over the 3Made of 0, a decimal point, 3 and U+0307. Not a rate: a dot over a digit marks a decimal that repeats without end.