Diptotes in Arabic (اَلْمَمْنُوعُ مِنَ الصَّرْفِ)

Diptotes are not that scary. They consist of a few rules about how their case ending changes - which means their I`raab - and groups of words which follow these rules. Understand the rules and you can spot a diptote from a mile.
You do need an intermediary understanding of Arabic grammar and language rules before learning about diptotes. Just FYI.

These types of words are partially declining words, or we can call them Diptotes in English to be posh, and اَلْمَمْنُوعُ مِنَ الصَّرْفِ in Arabic [Mamnu minas-sarf].

THE GOLDEN RULE:

All Arabic nouns (اسم) are in the Raf`a state by default (Raf`a = nominative = Dhamma at end). This means they naturally have 2 Dhamma's on the last letter as their I`raab.  The I`raab of these Isms then change according to whatever influential words come before it.

All normal happy regular nouns = Take all 3 different I`raabs.

But diptotes = only take 2 of the possible case endings. Diptotes do not have Tanween i.e.: no double vowel sign in any case.
Diptotes never take a Kasra. They're like allergic or something.

8 REASONS WHY SOME WORDS ARE DIPTOTES:

1. Feminine proper nouns do not have a Tanween as I`raab, which means no double vowel as a case ending on the last letter. Examples: Fatimah (فَاطِمَةُ), Hasnaa (حَسْنَاءُ), Hamda (حَمْدَى). These are names. In speaking we don't say the last vowel anyway (Fatima'u..?) but in text it can be written. Diptote ü
2. Feminine proper nouns (names) without an Alif (ا) and masculine proper nouns, both ending in a "Taa marbutah" (ةُ). These don't end with Tanween. Example: Hamzah (حَمْزَةُ). Diptote ü
3. Nouns and adjectives in the pattern of Af`alu (أَفْعَلُ) - which are also called Ism Tafdeel, the Superlative Verbs. Example: Akbaru, Anwaru (أَنْوَرُ), Afsaru (أَصْفَر), Diptote ü
4. Adjectives on the pattern of Fu`laanu (فَعْلاَنُ) never end with a Tanween. Example: `Uthmaan.
5. Non-Arabic names called `Ujma/`Ajami (عجمي), i.e all the foreign names, including Hebrew, English etc. Examples: Ibrahim (إبراهيم), Ismaeel (إسماعيل), Yaqoob (يعقوب) - Hebrew names. Pakistan (بَاكِسْتَانُ). Diptote ü
6. Compounds = putting two hyphenated words together as a proper noun. This happens often in the English language, and is used for cities. Examples: Hadra'maut (حضرموت), New York (نيو يورك). Diptoteü
7. Plural Arabic words never take a Kasra as I`raab and therefore they are dipotes! Diptote ü
8. Some broken plurals are also diptotes. Examples: Mosques (مَسَاجِدُ), Keys (مَفَاتِيحُ), Birds (ابابيل). Diptote ü

*Note: All Arabic colours are diptotes for following the pattern of bullet point 3.

DIPTOTE RULES RECAP

ØDiptote never takes Tanween.
ØIf the word begins with Alif-Laam = it's no longer a diptote.
ØWhen the diptote word is in a Majroor state, it will end with a Fat'ha, not a Kasra.
ØIf the diptote word becomes Mudaf in a sentence, it's no longer a diptote.

More like this: 

- The Mudaaf & Mudaaf Ilayhi (مضاف + مضاف اليه)

- Almost Every Tajweed Rule Poster

- How To Learn Surah Al-Qari`ah in 5 Steps