The phrase "second half" can be substituted with several synonyms depending on the context and the intended meaning. For example, "latter half," "end of the game," "final period," and "concluding segment" are some of the synonyms that can be used in sports. In the context of chronology, "last part," "ending phase," "concluding half," and "final stretch" are some of the alternatives. For a speech or presentation, one could use "concluding remarks," "ending portion," or "the summing-up" in place of "second half." It's always essential to use the right synonym to avoid confusion and relay a clear and precise message to your audience or readers.