But first, I want to give some infos about Turkish language and its history, to be able to understand it easier
Turkish is spoken as a native language by over 77 million people worldwide.
Language family: Altaic => Turkic => Southwestern Turkic => Western Oghuz => Turkish (Anatolian Turkish)
Writing system: Latin alphabet ( Turkish variant )
Turkish is official language in Turkey, Northern Cyprus and Cyprus. It is recognized regional language in Kosovo and Macedonia, and recognized minority language in Romania and Iraq.
Turkish language is regulated by Turkish Language Association, that was found by Kemal Ataturk.
The roots of the language can be traced to Central Asia, with the first known written records dating back nearly 1,300 years. ( Göktürks )
To the west, the influence of Ottoman Turkish (the variety of the Turkish language that was used as the administrative and literary language of the Ottoman Empire) spread as the Ottoman Empire expanded. In 1928, as one of Atatürk's Reforms in the early years of the Republic of Turkey, the Ottoman script was replaced with a phonetic variant of the Latin alphabet. Concurrently, the newly founded Turkish Language Association initiated a drive to reform the language by removing Arabic and Persian loanwords in favor of native variants and coinages from Turkic roots.
The distinctive characteristics of Turkish are vowel harmony and extensive agglutination.
The basic word order of Turkish is Subject Object Verb. Turkish has no noun classes or grammatical gender. Turkish has a strong T-V distinction and usage of honorifics. Turkish uses second-person pronouns that distinguish varying levels of politeness, social distance, age, courtesy or familiarity toward the addressee. The plural second-person pronoun and verb forms are used referring to a single person out of respect. In very formal situations, double plural second-person "sizler" may be used to refer to a much-respected person.
Old Turkic language ( Orkhun language, Gokturkish )
Old Turkic is the earliest attested form of Turkic, found in Göktürk and Old Uyghur inscriptions dating from about the 7th century to the 13th century.
The Old Uyghur language is not a direct predecessor the Uyghur language, though it is often considered to be a predecessor of the modern Western Yugur language. Old Turkic is attested in a number of scripts, including the Orkhon-Yenisei runiform script, the Old Uyghur script (a form of the Sogdian alphabet), the Brāhmī script, and the Manichean alphabet. Old Turkic is sometimes considered as belonging to the Southeastern branch of Turkic.
Old Turkic script
Old Turkic script ( aka Gokturkish, Orkhon ) is the alphabet used by the Göktürk and other early Turkic Khanates from at least the 8th century to record the Old Turkic language.
It was later used by the Uyghur Empire. Additionally, a Yenisei variant is known from 9th-century Kyrgyz inscriptions, and it has likely cousins in the Talas Valley of Turkestan and the Old Hungarian script of the 10th century.
Orkhon tablet:
Kök Tengri / Gök Tengri ( Sky God ) in Göktürk script
Let's look at the difference between Gokturkish and Anatolian Turkish:
Gokturkish: Üze Tengri basmasar, asra yir telinmeser, Türk budun ilingin törüngün kim artati udaçı erti ?
Anatolian Turkish: Üstte Tanrı basmasa, altta yer delinmese, Türk ulusu, ilini töreni kim bozabilecekti ?
English: Unless the sky (god) collapsed, the earth was pierced, Turkish nation, who could destroy your land and your tradition ?
Ottoman Language
Ottoman Turkish ( lisân-ı Osmânî ) is the variety of the Turkish language that was used as the administrative and literary language of the Ottoman Empire.
It borrows extensively from Arabic and Persian and was written in a variant of the Arabic script. Consequently, Ottoman Turkish was largely unintelligible to the less-educated lower-class and rural Turks, who continued to use kaba Türkçe or "rough Turkish", which used far fewer foreign loanwords and which is the basis of the modern Turkish language.
NOTE: Arabic and Persian scripts were used at the Ottoman Palace, but Anatolian people used to speak Anatolian Turkish without Arabic and Persian influences.
Difference between Ottoman Turkish and Anatolian Turkish
Ottoman Turkish:
Bu şehr-i Sıtanbûl ki bî-misl-ü behâdır
Bir sengine yekpâre Acem mülkü fedâdır
Anatolian Turkish:
Bu İstanbul şehrinin dünyada eşi benzeri yoktur
Tek bir taşına, tüm İran diyarı feda olsun
English:
O city of Istanbul, priceless and peerless!
I would sacrifice all Persian (Iranian) lands for one of your stones!
Language Reform and Modern Turkish
After the foundation of the Republic of Turkey and the script reform, the Turkish Language Association (TDK) was established in 1932 under the patronage of Mustafa Kemal Atatürk, with the aim of conducting research on Turkish. One of the tasks of the newly established association was to initiate a language reform to replace loanwords of Arabic and Persian origin with Turkish equivalents. By banning the usage of imported words in the press, the association succeeded in removing several hundred foreign words from the language. While most of the words introduced to the language by the TDK were newly derived from Turkic roots,
it also opted for reviving Old Turkish words which had not been used for centuries.
Owing to this sudden change in the language, older and younger people in Turkey started to differ in their vocabularies. While the generations born before the 1940s tend to use the older terms of Arabic or Persian origin, the younger generations favor new expressions. It is particularly ironic that Atatürk himself, in his lengthy speech to the new Parliament in 1927, used a style of Ottoman which sounded so alien to later listeners that it had to be "translated" three times into modern Turkish: first in 1963, again in 1986, and most recently in 1995. There is also a political dimension to the language debate, with conservative groups tending to use more archaic words in the press or everyday language.
Atatürk's teaching the people new Turkish at Gulhane Park
The past few decades have seen the continuing work of the TDK to coin new Turkish words to express new concepts and technologies as they enter the language, mostly from English. Many of these new words, particularly information technology terms, have received widespread acceptance. However, the TDK is occasionally criticized for coining words which sound contrived and artificial. Some earlier changes—such as bölem to replace fırka, "political party"—also failed to meet with popular approval (fırka has been replaced by the French loanword parti). Some words restored from Old Turkic have taken on specialized meanings; for example betik (originally meaning "book") is now used to mean "script" in computer science.
Many of the words derived by TDK coexist with their older counterparts. This usually happens when a loanword changes its original meaning. For instance, dert, derived from the Persian dard (درد "pain"), means "problem" or "trouble" in Turkish; whereas the native Turkish word ağrı is used for physical pain. Sometimes the loanword has a slightly different meaning from the native Turkish word, creating a situation similar to the coexistence of Germanic and Romance words in English (see List of Germanic and Latinate equivalents). Among some of the old words that were replaced are terms in geometry, cardinal directions, some months' names, and many nouns and adjectives.
Türk gençliği olarak önce dilimizi korumalıyız. 
Gümüş...Yaprak Dökümü... 
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