The Dual: Exactly Two

Frequently asked questions

When is The Dual: Exactly Two used?

English says "two books" with a number word. Arabic has a separate ending for exactly two, the dual, and for two things it uses this ending, not the plural. كِتابٌ is "a book", كِتابانِ is "two books": the ending already says "two".

How is The Dual: Exactly Two formed?

At the end of a phrase the final vowel is dropped in speech, so you will hear kitābān and kitābayn. أَخ is irregular: its dual brings back a hidden و, أَخَوانِ . Learn it as a word. An adjective copies everything from its noun, number included: غُرْفَتانِ كَبيرَتانِ - two big rooms; البَيْتانِ الجَديدانِ - the two new houses. A singular adjective after a dual noun is a mistake. Verbs have dual forms as well: هُما يَسْكُنانِ في دِمَشْقَ - the two of them live in Damascus. At A1, recognise them when you read; the verb paradigm comes later. اِثْنانِ exists, but not in front of the noun: *اِثْنانِ كِتاب is wrong. It may follow the noun for emphasis: كِتابانِ اثْنانِ - two books (not three).

What are common mistakes with The Dual: Exactly Two?

1. Using the plural for two: *كُتُب about two books. Use the dual: كِتابانِ. 2. Adding the number word as in English: *اِثْنانِ كِتاب. The ending is the number. 3. Not opening ة: *سَيّارَةانِ. Say سَيّارَتانِ. 4. A singular adjective after a dual noun: *غُرْفَتانِ كَبيرَةٌ. Say غُرْفَتانِ كَبيرَتانِ. 5. -āni after a preposition: *مَعَ صَديقانِ. Say مَعَ صَديقَيْنِ. English speakers: English expresses two with a separate word - "two", "both", "a pair of" - so when reading, the -ān / -ayn ending is easy to take for a plural. Look at the ending, not for a number word.

Sources

1. W. Wright, A Grammar of the Arabic Language, Vol. I (3rd ed., rev. W. Robertson Smith and M. J. de Goeje) — Cambridge University Press, 1896

   §§ 298-299 (pp. 187-188): nouns have three numbers, singular, dual and plural; the dual is formed by adding -āni to the singular, and a singular in ة changes it to ت (Rem. a), which is the rule behind سَيّارَتانِ.

2. W. Wright, A Grammar of the Arabic Language, Vol. I (3rd ed., rev. W. Robertson Smith and M. J. de Goeje) — Cambridge University Press, 1896

   § 308 (2) (pp. 235-236): the dual has only two case endings, -āni for the nominative and -ayni for the genitive and accusative, the basis of كِتابانِ / كِتابَيْنِ.

3. W. Wright, A Grammar of the Arabic Language, Vol. II (3rd ed., rev. W. Robertson Smith and M. J. de Goeje) — Cambridge University Press, 1898

   § 97 (p. 236): اِثْنانِ is "not unfrequently placed, as an adjective, after a noun in the dual, to express the idea of duality more strongly", which is the only place this article allows it: كِتابانِ اثْنانِ.

4. A Reference Grammar of Modern Standard Arabic (Karin C. Ryding) — Cambridge University Press, 2005

   Chapter 7, "Noun inflections" (pp. 119-204), is the modern reference treatment of number and case on MSA nouns, including the dual. Cited from the publisher's catalogue record; the chapter text was not consulted.