Swahili is a Bantu language with a lot of borrowed words from Arabic; as a result, the Swahili language is often thought to be a resultant language from the interaction between the Arabs and Bantus.

This is not true for Swahili existed even before the arrival of the first visitors on the East Africa coast who were Arabs as noted by historians like Grenville. According to Grenville, an Arab explorer and trader Ibn Batutta who was among the first explorers on East African coast had visited towns of Zeila, Mogadishu, Mombasa, Kilwa and Swahili land.

Therefore, Swahili land is a geographical area of Swahili speakers.

                Evidence from oral literature supports the fact that Swahili was in existence even before interaction from other cultures. The oral literature of Kilwa island was written in the 16th century and it explains that the first leader, Sultan Ali ibn Hussein, was nicknamed nguo nyingi  translated as many clothes. These are Swahili words and definitely the people of this area spoke Swahili. Creative works ranging from poems and epics to songs and narratives were created in a dialect (Swahili) which had a similar structure as other Bantu languages.

Like many other languages, there are many theories explaining the origin and nature of Swahili. However, the most common ones include

(1)          The theory that views Swahili as an Arabic language or dialect.

(2)          The theory that looks at Swahili as a mixture of Arabic and Bantu languages, and

(3)          The theory that explains Swahili as a Bantu language.

Those from the school of thought that Swahili is an Arabic language are guided by the facts that many words in the Swahili language are from  Arabic and that many people at the coastal strip are Muslims.

They argue that Islam was brought to the people of East African coast by the Arabs and so the language used to spread Islam (Swahili) could have been brought by the Arabs.

On the other hand, those who think Swahili is a language born out of the interaction between the local Bantu languages and Arabs fall into two categories.

The first group argues that  Swahili came into existence as a result of intermarriage between Arab men and Bantu women and so as a result a mixed language with both Arabic and Bantu characteristics came about (swahili).This is further strengthened by a historian  Grey (1962) in his work where he explains that Arab sailors were used to spending much time in different places at the coast and the islands. Therefore, Arab men married women from the local tribes and this led to a people of mixed race and language i.e. the Swahili people and the Swahili language. Those who support this theory believe that a Swahili speaking person (Mswahili) must be of an Arabic father and a Bantu mother and that Swahili is a mixture of Arabic and Bantu languages.

The second group which supports that Swahili is a mixed language maintains that Swahili language is a resultant language from the interaction between the Arabic and African languages and not specifically Bantu people. The supporters of this argument however do not specify these African languages and thus this argument is less convincing of them all.

The last, most common and correct theory views Swahili as a Bantu language.  According to the supporters of this argument, Swahili was in existence as a Bantu language even before the coming of the Arabs. The Swahilis people were then known as Wangozi and their language was known as Kingozi. The Wangozi interacted with different foreigners though this did not change their language or their identity. This view groups the Swahili with all the other African languages and mostly of Bantu origin .They argue that as much Swahili has a lot of borrowed words from other languages, more so Arabic is not reason enough  to disqualify it as a Bantu language. Very many borrowed words in Swahili are as a result of interaction between the inhabitants of the East African coast and the Arabic, Indian and Persian traders.

A linguist, Malcolm Guthrie in his research work, Comparative Bantu, examines Bantu languages. He is the one who first came up with the concept of proto Bantu. Proto Bantu is assumed to be an abstract language from which all the Bantu languages originate.  From his research, Swahili is proven to be a Bantu language that shares the same proto language with the other Bantu languages.

The Swahili morphology is similar to that of other Bantu languages. For example, when constructing a syllable just like in all other Bantu languages there are seven structures i.e.

(1)          Consonant and vowel e.g. dada(sister)

(2)          Syllables formed from vowels only e.g. oa(marry)

(3)          Syllables formed from consonants only e.g. mtu(person)

(4)          Syllables formed from more than one consonants and vowel e.g.ngoja (wait)

(5)          Syllables formed from a consonant semi vowel and a vowel e.g. mwalimuI (teacher)

(6)          Syllables formed from two consonants a semi vowel and a vowel eg mbwa (dog)

Bantu languages have nouns that are grouped into different categories known as noun classes. These divisions are based on grammatical agreement in a sentence brought about by subject noun agreement; Swahili has noun classes which also rely on subject noun agreement.

Lastly, the fact that Swahili language has five vowels (a,e,i,o,u) just like many other Bantu languages qualifies it to be a Bantu language.

Swahili language spread and became an East African lingua franca through factors like trade, religion, internal strife, administration and education.