In its most obvious, and often nonlegal meaning, sanear refers to repairing or remedying something, as per the simple definition appearing in the DLE: “reparar o remediar algo.” Saneamiento is often used with this meaning in legal contexts. For example (and these are certainly not the only legal meanings of the term), saneamiento contable may refer to a “write-down” of the value of an asset or a “write-off” of losses or a debt. Saneamiento financiero may denote some type of “financial restructuring (or) streamlining,” while saneamiento monetario often refers to “monetary reform.” And, as a final example, saneamiento ambiental may describe some type of “environmental remediation” or “environmental clean-up.”
But saneamiento appears in other legal contexts in which its meaning is not always so obvious. In the Spanish law of obligations (Derecho de obligaciones) the expression obligación de saneamiento generally refers to some type of “warranty obligation,” defined in the DEJ as “responsabilidad que asume el vendedor frente al comprador respecto de la posesión pacífica y útil del objeto vendido y de su ideoneidad para el uso que le es propio.”
The Spanish Civil Code provides for three types of saneamiento warranties. First, under saneamiento por evicción (Art. 1475 CC), seller warrants that buyer will enjoy undisturbed legal possession of purchased property, unopposed from someone claiming paramount rights (mejor derecho). Here evicción denotes “loss of title” (by judicial decision), and saneamiento por evicción may thus be translated as “warranty of title,” “warranty of good title,” or “warranty against loss of title.” When saneamiento por evicción refers to leased (rather than purchased) property, “warranty of quiet enjoyment” would provide an appropriate rendering.
Saneamiento por cargas o grávamenes ocultos (Art. 1483 CC) is a second type of warranty obligation in which seller warrants to buyer that property sold or otherwise transferred is free of charges, liens or other encumbrances. In this context a possible translation might be “warranty of clear title” or “warranty against hidden charges/liens/encumbrances.”
And under a saneamiento por vicios ocultos obligation (Art. 1484 CC) seller warrants to buyer that the property or goods sold are free from hidden or latent defects, usually undertaking to repair or replace any items found to be defective. This may often be translated as “warranty against hidden/latent defects.”
From the above, it is clear that “eviction” and evicción are “false friends.” Read more here.