Falta vs. ausencia vs. carencia vs. escasez

The Spanish language offers nuanced ways to express the notion of lack or shortage, with words like 'falta', 'ausencia', 'carencia' and 'escasez'. While they all share similar meanings, their specific uses vary.

Falta

Falta generally refers to the absence of something necessary or expected. This can refer to a person, object, or concept.
Me falta dinero para el alquiler.
(I lack the money for rent.)
Hubo una falta de comunicación entre ellos.
(There was a lack of communication between them.)

Ausencia

Ausencia is used to indicate when something is missing or not present, it is often used more in relation to physical presence of people or things.
Su ausencia en la ceremonia fue notable.
(His absence at the ceremony was noticeable.)
La ausencia de agua podría ser un problema.
(The absence of water could be a problem.)

Carencia

Carencia usually means an insufficient quantity of something, it implies the need or desire for what is missing. It's frequently used in a socio-economic context.
Los niños sufren de carencia alimenticia.
(The children suffer from nutritional deficiency.)
Hay una carencia de empleos en este lugar.
(There is a lack of jobs in this place.)

Escasez

Escasez implies a rarity or short supply, typically referring to resources and commodities. It suggests that demand outstrips supply and is frequently used in economical contexts also.
Hubo escasez de agua durante la sequía.
(There was a scarcity of water during the drought.)
Hay escasez de alimentos en el mercado debido al bloqueo del tráfico.
(There is a shortage of food in the market due to traffic blockade.)

Summary

While 'falta', 'ausencia', 'carencia', and 'escasez' all deal with the theme of insufficiency or absence, they are used alone based on different conditions and contexts; 'falta' refers primarily to an expected absence, 'ausencia' emphasizes physical non-presence, 'carencia' indicates a deficiency or need, and 'escasez' signals an inadequate supply in relation to demand.