It is sometimes difficult to separate concepts in Islam from concepts specific to Arab culture, from the language itself. The Qur'an is expressed in Arabic and traditionally Muslims deemed it untranslatable, though this view has changed somewhat in recent decades. Concepts that derive from both Islam and Arab tradition, which are expressed as words in the Arabic language, and are sufficiently specific to these to require their own articles here, are:
A
adab - describes one's behaviour. For example, following the hadith rules is good adab.
awra - the part of a person's body that must be covered before everybody but a spouse. It may also be used to refer to what must be concealed of a woman before non-related men
ayah (plural ayat) - a sign. More specifically a verse in the Qur'an
'azl - coitus interruptus, intercourse characterized by withdrawal of the penis before ejaculation
dhimmi - Jews and Christians (and sometimes others,), whose right to practice their religion is tolerated within an Islamic society, but with lower legal status. Dhimis are freed from conscription and have pay less tax than muslim. If they choose to join the army, they are totaly freed from the obligation of paying taxes for the rest of their life.
hanif - the 5 monotheist prophets, namely Prophet Adam, Prophet Abraham/Ibrahim, Prophet Moses/Musa, Prophet Jesus/Isa and Prophet Muhammad.
haram - (with a long a) forbidden. Antonym halal. (with a short a) sanctuary.
hijab - describes the self-covering of a woman's body for the purposes of modesty and dignity. A woman must conceal her hair and body from the sight of all men except her husband and immediate relatives. However, hijab is more than the thickness of the cloth that covers the body; hijab should be a system of behaviour of modesty and dignity.
hijra - literally migration, Muhammad's and his followers' emigration from Mecca to Medina
hudud - Literally, limits or boundaries. Usually refers to limits placed by God on man; penalties of the Islamic law which are described in the Qur'an
I
ibadah - worship, but not limited to ritual: all expressions of servitude to Allah from pursuit of knowledge living a pious life, helping, charity, humility
ihram - state of consecration for haj. Includes dress and or prayer.
ijma - the consensus of either the ummah (or just the ulema) - one of four bases of Islamic Law. More generally, political consensus itself.
ijtihad - during the early times of Islam the possibility to find a new solution to a juridical problem. Has not been allowed in conservative Islam since the Middle Ages.
imam - literally leader, e.g. a man who leads a community or leads the prayer; the Shi'a sect use the term only as a title for one of the twelve God-appointed successors of Prophet Muhammad.
imamah /imamate - Successorship of Prophet Muhammad and the leadership of mankind. Shi'as regard this as the fourth Pillar of Islam.
Intifada - An uprising among Palestinian Arabs of the Gaza Strip and West Bank, beginning in late 1987 and continuing sporadically into the early 1990s, in protest against continued Israeli occupation of these territories.
jahiliya - the time of ignorance before Islam was realized. Describes polytheistic religions.
jamia - "gathering", at university, at a mosque for jumuah prayer, etc.
jilbab - long outergarment
jihad - struggle. Any earnest striving in the way of Allah, involving personal, physical, intellectual or military effort, for righteousness and against wrong-doing;
"Lesser Jihad": fighting to protect Islam from attack or oppression. In such fighting, no woman, child or innocent civilian is to be harmed, and no tree is to be cut down. Shi'as believe that only Prophet Muhammad and the twelve Imams had authority to declare positive jihad of the lesser kind.
"Greater Jihad": internal struggle for the soul (nafs ) against evil, e.g. to overcome the temptation to sleep when it is time to pray the morning prayer is a greater jihad.
khalifa - Man's trusteeship and stewardship of Earth; Most basic theory of the Caliphate; Flora and fauna as sacred trust; Accountability to God for harms to nature, failure to actively care and maintain. Three specific ways in which khalifa is manifested in Muslim practice are the creation of haram to protect water, hima to protect other species (including those useful to man), and by resisting infidel domination over Muslim lands, in jihad.
kufr - the manifestion of not believing in God, aspects of God's law, names and attributes.
L
la'nat - curse
M
madhab - school of religious jurisprudence, school of thought
mahdi - "a guide". More specifically al-Mahdi (the guide) is a figure who will appear with Prophet Jesus before the end of time, when God allows it, to bring world peace, order and justice, after it has been overcome with injustice and aggression. The Shi'as regard the twelth Imam as the Mahdi. The Sunnis regard someone else as the Mahdi.
mahram - a relative of the opposite gender usually described as being "within the forbidden limits"; a better description is "within the protected limits". means relatives who one can appear before without observing hijab and who one cannot marry.
masum - a person who does not commit sins, does not make mistakes, does not forget, etc. although he/she does have the choice to commit sins. The Shi'as regard Prophet Muhammad, his daughter (Fatimah) and the twelve Imams to be the fourteen Masumin.
me'ad - the Resurrection; God will resurrect all of humankind to be judged. Shi'as regard this as the fifth Pillar of Islam.
qiyas - analogy - foundation of legal reasoning and thus fiqh
Qur'an - Muslims believe that the Qur'an is the literal word of God and culmination of God's revelation to mankind, revealed to Muhammad in the year 610 A.D.
S
salah/salat - any one of the 5 daily obligatory prayers. Sunnis regard this as the second Pillar of Islam
shahadah - The expression of faith: La ilaha illa Allah ("There is no god but God"). Sunnis regard this as the first Pillar of Islam
shaheed - "witness". More specifically refers to a person killed whilst striving in Islam, a martyr. Often used in modern times for deaths in a political cause (including victims of soldiers, deaths in battle, suicide bombers, etc.)
sufi - a Muslim mystic; Sufism (tasawwuf) is a fairly recent sect in Islam.
sunnah - "path" or "example"; sunnah annabi is what the Prophet has done or said or agreed to; He is considered as the best human moral example by Muslims, the best man to follow;
sunni - the largest sect in Islam, having no single central authority
sura - chapter; the Qur'an is comprised of 114 suras
T
tafsir - exegesis, particularly such commentary on the Qur'an
tajwid - special manner of reading the Qur'an. When you do it, you get more rewards for your reading.
taqlid - blind imitation of precedent, normally of a classical jurist of fiqh, contrast to ijtihad and ijma which imply status for the community and lay public.
taqiyya - the mostly Shi'a principle that one is allowed to hide one's true belief in certain circumstances.
ulema or ulama - the leaders of Islamic society, including teachers, Imams and judges
ummah or umma - the global community of all Muslim believers; international personhood of Islam
urf - custom of a given society, leading to change in the fiqh
W
wahdat al-wujud - "unity of being". Philosophical term used by some Sufis. Related to fana
warraq - traditional scribe, publisher, printer, notary and book copier
Z
zakat - tax, alms, tithe as a Muslim duty; Sunnis regard this as the fourth Pillar of Islam. Neither charity nor derived from Islamic economics, but a religious duty and social obligation.
zina - sexual activity outside marriage (covering the English words adultery and fornication)
NOTE: Wikipedia is not a general Arabic-to-English dictionary. The list above includes only those concepts sufficiently specific to Islam or Muslim culture to merit their own full articles. The prime purposes of this list are to disambiguate multiple spellings, make note of spellings no longer in use for these concepts, define the concept in one line to make it easy to pin down the one you're looking for, and provide a guide to unique concepts of Islam all in one place.
There is an English/Arabic dictionary on wiktionary.
Arabic numerals are what we use in English ("0", "1", "2",...). The modern Arabs in Arabia generally use the Hindi numerals.
Some English words or phrases would translate very poorly into Arabic for cultural reasons, for instance the English word "crusade" would most likely be interpreted as meaning "genocide", and "infinite justice " would most likely be interpreted as meaning "divine judgement " - adl in Arabic implying Allah's justice. Probably it is best to avoid such terms for anything one intends to translate into Arabic, or knows will be translated.
Some Islamic concepts are usually referred to in Persian or Turkic. Those are typically of later origin that the concepts listed here - for completeness it may be best to list Persian terms and those unique to Shi'a on their own page, likewise Turkic terms and those unique to the Ottoman period on their own page, as these are culturally very distinct.
References
Suzanne Haneef , What Everyone Should Know about Islam and Muslims, (Kazi Publications, Chicago), popular introduction
