Turkish/Loanwords

Like every natural language Turkish has many loanwords. A good indicator of whether a word is original Turkish or a loanword is to look at the vowels in the word. If the word internally doesn't follow vowel harmony, you know it's probably a loanword. Also, if you find two vowels right next together within a word (impossible in standard Turkish) or long vowels, then it's a loanword. This is one of the biggest problems Turkish speakers have with English. They can't figure out how to pronounce words that don't follow the rules they've been using their entire lives. The most ancient layer of loanwords in Turkish are words borrowed from Mongolian, another East Asian language that has vowel harmony and many of the same sound rules, so these loanwords can be more difficult to identify; however, there are relatively few of them.

Arabic

 * aile - عائلة - family
 * bina - بناء - building
 * beyaz - أبيض - white
 * ceviz - جوز - walnut
 * din - دين - religion
 * hayat - حياة - life
 * insan - إنسان - human
 * kahve - قهوة - coffee
 * kalem - قلم - pen
 * kalp - قَلْب - heart
 * kitap - كتاب - book
 * mektup - مكتوب - letter
 * sabah - صباح - morning
 * sebep - سبب - reason
 * sel - سيل - flood
 * takvim - تقويم - calendar
 * zaman - زمان - time
 * zeytin - زيتون - olive

French

 * kuaför - coiffeur - hairdresser
 * argo - argot - slang
 * randevu - rendez-vous - meeting
 * bisiklet - bicyclette - bicycle
 * asansör - ascenceur - elevator
 * pantolon - pantalon - trousers
 * kravat - cravate - tie (clothing)
 * lavabo - lavabo - washbasin
 * tuvalet - toilette - toilet
 * banliyö - "banlieue" - suburban (train)
 * mizanpaj - mise-en-page - layout
 * sütyen - soutien-gorge - bra
 * müzisyen - musicien - musician
 * orgazm - orgasm

Persian

 * birader - برادر - brother
 * çehre - چِهرِه - face
 * dut - توت - mulberry
 * dürbün - دوربین - binoculars
 * hafta - هَفتِه - week
 * lacivert - لاجورد - navy blue
 * Perşembe - پَنج‌شَنبِه - Thursday
 * sade - سادِه - plain
 * şah - شاه - king
 * şehzade - شاهزادِه - prince
 * siyah - سياه - black

Turkish loanwords
English, and many other languages, have taken some words from Turkish:
 * yogurt (yoğurt)
 * kebab or shish kebab (kebap or şiş kebap)
 * baklava (baklava)
 * caviar (havyar)
 * pastrami (pastırma)
 * bergamot (bey armudu)
 * bulgur (bulgur)
 * caracal (karakulak)
 * dolman (dolaman)
 * gilet - jelick (yelek)
 * horde (ordu)
 * Janissary (Yeniçeri)
 * kefir (kefir)
 * kielbasa (külbastı)
 * lackey (ulak)
 * latten (altın)
 * odalisque (odalık)
 * pierogi (börek)
 * sarma (sarma)
 * shabrack (çaprak)
 * turquoise (turkuaz)
 * Dolmetscher (dilmaç)
 * Богатыр (batur)
 * μπουζούκι (bozuk)
 * καΐκι (kayık)
 * kessar (kaşar)
 * tiorba (torba)