A|| B|,| A±B|≤| A|+| B|,|| A|—| B||≤| A±B| and| Re A|≤| A|(among others) hold in an
unbounded operator setting. As consequences, we obtain a characterization of (unbounded)
self-adjointness as well as a characterization of invertibility for the class of unbounded
normal operators. Some examples accompany our results.