Swahili (Kiswahili) is a Bantu language spoken by various ethnic groups that inhabit several large stretches of the Mozambique Channel coastline from northern Kenya to northern Mozambique. Swahili serves as a national, or official language, of four nations: Tanzania, Kenya, Uganda, and the Democratic Republic of the Congo. It is used as a lingua franca in much of East Africa, and the total number of speakers exceeds 140 million. Standard Swahili has five vowel phonemes: /ɑ/, /ɛ/, /i/, /ɔ/, and /u/. Swahili is currently written in a slightly defective alphabet using the Latin script; the defectiveness comes in not distinguishing aspirated consonants, though those are not distinguished in all dialects. It has also incorporated Persian, German, Portuguese, English, and French words into its vocabulary through contact with empire builders, traders, and slavers during the past five centuries.