Two postcolonial varieties, two different sounds
Both Indian and Nigerian English share British-spelling heritage and syllable-timed rhythm, but the phonologies are distinct. Indian English uses retroflex consonants — /t/ and /d/ produced with the tongue curled back — which Nigerian English does not. Nigerian English has a more reduced vowel inventory than Indian English. The "th" sounds differ too: Indian English often uses aspirated dental [t̪ʰ]/[d̪ʰ]; Nigerian English usually uses plain [t]/[d].
