What is trespass, legally speaking? How about a nuisance?

TRESPASS AND NUISANCE DEFINED (Tex. 2011)

Trespass to real property is an unauthorized entry upon the land of another, and may occur when one enters—or causes something to enter—another’s property. See Coastal Oil & Gas Corp. v. Garza Energy Trust, 268 S.W.3d 1, 11 n.29 (Tex. 2008); Glade v. Dietert, 295 S.W.2d 642, 645 (Tex. 1956). "[E]very unauthorized entry upon land of another is a trespass even if no damage is done or injury is slight." Coastal Oil, 268 S.W.3d at 12 n.36 (quoting McDaniel Bros. v. Wilson, 70 S.W.2d 618, 621 (Tex. Civ. App.—Beaumont 1934, writ ref’d) (alteration in original)).

A nuisance is a condition that substantially interferes with the use and enjoyment of land by causing unreasonable discomfort or annoyance to persons of ordinary sensibilities. Schneider Nat’l Carriers, Inc. v. Bates, 147 S.W.3d 264, 269 (Tex. 2004); see also Burditt v. Swenson, 17 Tex. 489 (1856).

The common definition of damage is "loss due to injury: injury or harm to person, property, or reputation." WEBSTER’S THIRD NEW INTERNATIONAL DICTIONARY 571 (2002).

SOURCE: TEXAS SUPREME COURT - 10-0669 - 10/21/11 - Barnes v. Mathis (Tex. 2011)
(per curiam opinion) 

ELEMENTS OF TRESPASS TO TRY TILE ACTION 

The Texas Property Code provides in part, "A trespass to try title action is the method for determining title to lands, tenements, or other real property." TEX. PROP. CODE ANN. § 22.001(a) (West 2014). 

"To prevail in a trespass-to-try-title action, a plaintiff must usually (1) prove a regular chain of conveyances from the sovereign, (2) establish superior title out of a common source, (3) prove title by limitations, or (4) prove title by prior possession coupled with proof that possession was not abandoned." Wilhoite v. Sims, 401 S.W.3d 752, 760 (Tex. App.-Dallas 2013, no pet.).