Since pH is defined as the negative logarithm of the concentration of hydronium ions, acidic solutions thus have a pH of less than 7.
sˈɪns pˈiː ˈeɪtʃ ɪz dᵻfˈaɪnd æz ðə nˈɛɡətˌɪv lˈɑːɡɚɹˌɪθəm ʌvðə kˌɑːnsəntɹˈeɪʃən ʌv haɪdɹˈoʊniəm ˈaɪɑːnz, ɐsˈɪdɪk səlˈuːʃənz ðˈʌs hæv ɐ pˈiː ˈeɪtʃ ʌv lˈɛs ðɐn sˈɛvən.