What is the difference between an Emir and a Sultan?

Solution 1:

Entries from the OED provided below.

Note carefully the years that these words entered English:

• For example, emirate is extremely recent.

• You missed the eldest of terms, caliph, such as the exceedingly famous Caliphate of Córdova, which ruled Iberia and northern Africa between 929–1031.

• There is apparently no attested word ∗sheik(h)dom.

These are all taken from the online OED, and haven’t been updated since the second edition.

caliph | calif n. 1393

The title given in Muslim countries to the chief civil and religious ruler, as successor of Muhammad.

caliphate n. 1614

1. • a. The rank, dignity, or office of caliph.
   • b. The reign or term of office of a caliph
2. The dominion of a caliph.

sultan n. 1555

1. • a. The sovereign or chief ruler of a Muslim country; spec. (Hist.) the sovereign of Turkey. Also formerly, a prince or king's son, a high officer.

   • b. Taken as a type of magnificence; also attrib.

   • c. Used with allusion to an Eastern ruler's harem; also attrib.

2. An absolute ruler; gen. a despot, tyrant.

sultanate n. 1822

1. A state or country subject to a sultan; the territory ruled over by a sultan.

2. The office or power of a sultan.

sheikh n. 1577

1. • a. The chief of an Arab family or tribe; the headman of an Arabian village; an Arab chief; †an Eastern governor, prince, king. Now also used among Arabs as a general title of respect.
   • b. (Chiefly in spelling sheik.) A type of a strong, romantic lover; a lady-killer. [After The Sheik, a novel by E. M. Hull (1919), and its cinematic adaptation The Sheikh, 1921, starring Rudolph Valentino.]
2. • a. The head of a Muslim religious order or community; a great religious doctor or preacher; now esp. a saint having a local cultus.
   • b. Sheikh-ul-Islam (properly Sheikhu 'l Islam) : the supreme authority in matters relating to religion and sacred law; in Turkey, the mufti. Hence Sheikh-ul-Islamate.
3. In India, one of a dissenting sect of Muslims; a general term for Hindu converts to Islam. (Usually shekh, shaikh.)

emir n. 1625

1. A Saracen or Arab prince, or governor of a province; a military commander.
2. A title of honour borne by the descendants of the prophet Muhammad.

emirate n. 1863

The jurisdiction or government of an emir.