קִיר, חוֹמָה, כֹּתֶל
קִיר listen and repeat is the everyday word. It refers to the wall you're probably facing right now, if you're indoors. It's that which encloses and divides between rooms.
בַּחֶדֶר שֶׁנִּפְתַּח אֶל הֶחָצֵר יֵשׁ שְׁלֹשָׁה קִירוֹת וְדֶלֶת גְּדוֹלָה מִזְּכוּכִית.
In the room that opens to the yard there are three walls and a large glass door.
The word חוֹמָה listen and repeat refers to a wall that is meant to keep people and things from passing through, protecting that which is inside. While קיר is a wall in a private or community setting, חומה is the wall of a public place, such as a city:
יְהוּדִים בְּעָרִים מֻקָּפוֹת חוֹמָה מִימֵי קֶדֶם חוֹגְגִים אֶת פּוּרִים אַחֲרֵי כֻּלָּם.
Jews in cities surrounded by walls since ancient times celebrate Purim after everyone (else).
For some of you, the first Hebrew word that came to mind when you saw the title for today's entry, was כֹּתֶל listen and repeat, as this is the word used to describe the Western Wall or the Wailing Wall - הַכֹּתֶל הַמַּעֲרָבִי listen and repeat (literally, the Western Wall).
But while קיר and חומה appear frequently in Biblical Hebrew, כותל appears only once, and that in the poetic book of Song of Songs or Song of Solomon. From Biblical times until today, the word is used only in flowery or literary contexts, such as in the title of the nonfiction work by Tomer Einat:
שָׂפָה אֲסוּרָה: הַחַיִּים וְהַמִּלִּים בֵּין כָּתְלֵי הַכֶּלֶא
Forbidden Language: Life and Words Between the Prison Walls