The spelling of the phrase "is trail" is straightforward if you know the phonetic transcription. In IPA, "is" is pronounced as /ɪz/ with a short "i" sound and a voiced "z" sound. "Trail" is pronounced as /treɪl/ with a long "a" sound as in "ray" and a "l" sound at the end. If you're writing "is trail" in a sentence, make sure to double-check the spelling to avoid confusion with similar-sounding words like "his" or "it's."