nˈoʊt ðæt ɪn kˈɑːmən pˈɑːɹləns wɪðˌɪn lˈʌndən, ðə tˈɜːm "ˌoʊvɚɡɹˈaʊnd" mˈeɪ biː jˈuːzd ɪn ɹˈɛfɹəns tʊ ˌɛni nˈæʃənəl ɹˈeɪl lˈaɪn, ɪn ˈɔːɹdɚ tə dɪstˈɪŋɡwɪʃ ɪt fɹʌmðɪ ˌʌndɚɡɹˈaʊnd.
Note that in common parlance within London, the term "overground" may be used in reference to any National Rail line, in order to distinguish it from the Underground.