応援してるよ

The word '応援' (ōen) is a combination of '応' (ō), meaning 'respond' or 'answer', and '援' (en), meaning 'help' or 'support'. Together, they form the meaning of 'cheering' or 'supporting'. The verb 'してる' (shiteru) is a casual contraction of 'している' (shite iru), which is the continuous/progressive form of 'する' (suru - to do). The particle 'よ' (yo) adds a sense of emphasis or assurance.