Self-tutoring about English: the tutor checks a fact. Adaptor or adapter? Either one, apparently: both are correct and have the same meaning. Source: Mish, Frederick C. Merriam-Webster Dictionary. Springfield: Merriam-Webster, 2004.

Self-tutoring about spelling: the tutor shares a find. Tendinitis or tendonitis – which one is correct? Both are, it turns out: they mean the same. Source: Mish, Frederick C. (editor). Merriam-Webster Dictionary. Springfield: Merriam-Webster, 2004.

Self-tutoring about English: the tutor checks about esthetic and aesthetic. Apparently, aesthetic and esthetic have the same meaning. Source: Mish, Frederick C (editor). The Merriam-Webster Dictionary. Springfield: Merriam-Webster, 2004.