ˈɔːl ðə mˈiːnɪŋz ɑːɹ vˈɛɹi sˈɪmɪlɚɹ ɪn kˈɑːnsɛpt: ɪn kˈɛmɪstɹi, ðə tɹænsmˈɪʃən kˌoʊɪfˈɪʃənt ɹᵻfˈɜːz tʊ ɐ kˈɛmɪkəl ɹɪˈækʃən ˌoʊvɚkˈʌmɪŋ ɐ pətˈɛnʃəl bˈæɹiɚ; ɪn ˈɑːptɪks ænd tˌɛlᵻkəmjˌuːnɪkˈeɪʃənz ɪɾ ɪz ðɪ ˈæmplɪtˌuːd əvə wˈeɪv tɹænsmˈɪɾᵻd θɹuː ɐ mˈiːdiəm ɔːɹ kəndˈʌktɚ tə ðæt ʌvðɪ ˈɪnsɪdənt wˈeɪv; ɪn kwˈɔntəm mᵻkˈænɪks ɪɾ ɪz jˈuːzd tə dᵻskɹˈaɪb ðə bᵻhˈeɪvjɚɹ ʌv wˈeɪvz ˈɪnsɪdənt ˌɔn ɐ bˈæɹiɚ, ɪn ɐ wˈeɪ sˈɪmɪlɚ tʊ ˈɑːptɪks ænd tˌɛlᵻkəmjˌuːnɪkˈeɪʃənz.
All the meanings are very similar in concept: In chemistry, the transmission coefficient refers to a chemical reaction overcoming a potential barrier; in optics and telecommunications it is the amplitude of a wave transmitted through a medium or conductor to that of the incident wave; in quantum mechanics it is used to describe the behavior of waves incident on a barrier, in a way similar to optics and telecommunications.