mim

م

The Arabic letter mim can appear in four different forms: isolated, initial, medial and final.

finalmedialinitialisolated
ـمـمـمـم

When you show the letter on its own, you use the isolated form.

م

When the letter is the first letter of a word, you use the initial form.

مـ

For example these words:

bitter
murr
مُرّ
boredom
malal
مَلَل
death
mawt
مَوت

When the letter is not the first and not the last but somewhere in the middle of a word, you use the medial form in most cases.

ـمـ

For example these words:

wheat
qamH
قَمح
silence
Samt
صَمت
liquor
khamr
خَمر

When the letter is the last letter of a word, you use the final form in most cases.

ـم

For example these words:

referee
Hakam
حَكَم
arrow
sahm
سَهم
verdict
Hukm
حُكم

Now you know that:

In most cases...
Let us look at the other cases!

The letter mim has dual joining, like most Arabic letters. It wants to join with both the letter before it and the letter after it.
But some letters has right joining. They only want to join with the letter before it (which is the letter to the right since Arabic is written from right to left).

When the letter is in the middle of a word, and follows a right joining letter, you use the initial form.

مـ
throwing
ramy
رَمي
time
zaman
زَمَن
sand
raml
رَمل

When the letter is the last letter of a word, and follows a right joining letter, you use the isolated form.

م
bay
sharm
شَرم
sleep
nawm
نَوم
foot
qadam
قَدَم

Now you know that:

That's it!
The rules you just learned can be applied to all Arabic letters with dual joining, which is most of them.

Previous letter: lam ل Next letter: nun ن