In is the sixteenth letter of the Samaritan alphabet and carries the numeral value seventy. It stands where Hebrew has ayin, and it is the fourth and last of the throat letters whose consonants have weakened in the Samaritan reading tradition, which is why the letter name is In.
The consonant it once wrote is one of the hardest in the Semitic inventory for an outsider to hear or to make, a constriction deep in the throat for which English has no equivalent. Like it and zen, this letter carries more than one sound of the ancestor language, and the second one is preserved in Arabic with a letter of its own.
There is a well known piece of evidence for that merger, and it comes from Greek. When the Hebrew scriptures were translated into Greek, the translators sometimes rendered this letter with a g in a proper name, which makes no sense if the letter wrote only the sound it writes in later Hebrew, and complete sense if the older second sound was still audible in some words at the time. The name Gomorrah, which begins with this letter in Hebrew and with a g in Greek, is the standard example. It is a small thing and it is decisive, and it shows how a translation into another script can preserve information the original script had already stopped recording.
The character is encoded at U+080F.