Sri Lankan English (SLE) has unique phonological, morphological, lexical and syntactic features which have gradually developed since the introduction of English to Sri Lanka. Vocabulary is one of the first features to develop in SLE. Although the SLE vocabulary has been studied and recorded, its generational difference has not been examined. The objective of the study was to investigate if the ‘generational change' observable in the SLE vocabulary could be considered an evolution. This was done through a qualitative, comparative analysis of the vocabulary used in the decades 1955 – 1965 and 2005 – 2015. The theoretical base of the research was defined using two theories of language evolution: the apparent-time hypothesis and age-gradedness. The primary data was taken from the Ceylon Observer of the decade 1955 – 1965 and the Sunday Observer of the decade 2005 - 2015. The words were used in a questionnaire survey of 60 participants of which 30 were of the age 15 – 25 years and 30 were of the age 65- 75 years. The results of the survey were then analyzed in detail through 10 interviews. The surveys and the interviews were conducted to prove / disprove the age-gradedness of the SLE vocabulary and to prove / disprove the apparent-time hypothesis in relation to the SLE vocabulary. Most of the vocabulary used disproved age-gradedness. The usages of these terms were found to be generation specific, which supported that the SLE vocabulary is not age-graded. The interviews supported the apparent-time hypotheses as the older generation showed that their vocabulary has not changed significantly over the years. From these observations, it could be concluded that within the scope of the research, the generational difference observable in the SLE vocabulary over 60 years could be termed an evolution.