A research report submitted to the Faculty of Science, in partial fulfilment of the requirements for the degree of Master of Science, University of the Witwatersrand, Johannesburg, August 2014. / The science teacher’s language, in the science classroom, has become a new language built with familiar Language of Learning and Teaching (LOLT) words, in this case English. This research study investigated the learners’ ideas and understanding of simple everyday words when used in the physics classroom. The study focused on bringing to light the existence of the problem of contextual meanings of everyday words in the physics classroom language. The participants in this study were mainly English second language learners and educators from 5 high schools in the city of Johannesburg, South Africa, selected on the basis of their accessibility and socio-economic backgrounds. These consisted of 105 high school learner participants of physical science, (84 grade 11 learners and 21 grade 12 learners) and 5 physical science teacher participants (one from each school). The methods of data collection used were the questionnaire and the interview. The questionnaire items were developed using simple everyday words to test the learners’ understanding of every words when used in a physics context. The learners were interviewed soon after the questionnaire was marked. The respective physical science teachers were also interviewed to further probe on their learners’ answers. The findings in this study suggest that the learners have difficulties with the contextual meanings of everyday words when used in the physics classroom. The types of difficulties included learners assuming that certain words they meet in everyday life situations still carried the same meanings when they are used in physics contexts. The sources of the difficulties were that the learners thought they understood the science classroom language and the teachers also assumed that their learners understood this language. The findings also showed that the educators fail to notice that what seems clear and simple to them may be difficult and vague to their learners.