That's interesting.
For a word to be visually read left-to-right and right-to-left at the same time you have to have:
1- Each letter in the word is optically symmetric (the letter itself can be read left-to-right and right-to-left). e.g. A H I(i) l(small L) M O(o) T U V(v) W(w) X(x) Y. These are all the letters in English that have this character.
2- The number of the letters must be either odd, or even with the innermost two letters identical e.g. otto (male name)
So you can form words like MOM, WOW and you can read them the same in a mirror.
Arabic has the letters of a word connected, so every letter has 3 forms; one when the letter is written at the beginning of the word, one in the middle and one at the end. This allows for another case for mirror-imaged words:
- if you have one form of a letter, when you flip it you get one form of another letter e.g. لـ (the letter ل at the beginning) and ـا (the letter ا at the end). These are the only two forms of letters in Arabic that obey this rule.
So you can have words like:
لا meaning no
لنا "for us"
لما (lamma) one of its meanings is "when": لما أكلت when I ate
لها (laha) "for her"
لها (laha) plural of uvula (rarely used)
لها (loha) plural of gratuity (rarley used)
A part of an old Arabic poem says: اللها تفتح اللها (al loha tafta7 al laha). It means: gratuities make him satisfied.
لغا "what he said was void"
لنمنا "we would have slept" e.g. لو شعرنا بالتعب لنمنا if we were tired we would have slept. The root verb is نام (he slept)
لنمنمنا "we would have decorated (sth.)" (rarely used). The root verb is نمنم and it is commonly used with books and writings. لنمنمنا كتابتنا means we would have decorated our script.
لنهنهنا "فلان" عن "شيء means we would have rebuffed "sb" from doing "sth" (rarely used). The root verb is نهنه
The letters in Arabic that can be used in the middle of mirror-imaged words are: ـبـ (ب)، ـتـ (ت)، ـثـ (ث) ـسـ (س)، ـشـ (ش)، ـعـ (ع)، ـغـ (غ)، ـفـ (ف)، ـقـ (ق)، ـمـ (م)، ـنـ (ن)، ـهـ (ه)، ـيـ (ي