Half seconds are a measure of time that is equal to half a second. However, there are several other synonyms one could use to describe an interval of this duration. Some possible alternatives include "500 milliseconds," "0.5 seconds," "a split-second," "a moment," and "a blink of an eye." Each of these phrases evokes a slightly different mental image of the passing of time, with some emphasizing brevity and urgency while others suggest a fleeting or illusory quality. Ultimately, the choice of synonym will depend on the context in which the interval is being described and the effect that one wants to achieve with their words.