感到 (gǎn dào) means to feel or to sense, expressing internal emotional or physical perception. 感 relates to feeling and sensation, while 到 here acts as a result complement indicating that the feeling has been reached or registered. It is followed directly by an adjective or noun describing the feeling (感到高兴, feel happy; 感到痛, feel pain). It is similar to 觉得 (jué de) but often more formal.