The verb is a word by which we affirm something. It is the essential word in a sentence: without it (expressed or understood) no sentence can be construed.

Verbs are divided into Auxiliary, Transitive and Intransitive.

The Auxiliary verbs in Spanish are: Haber, Tener, Ser, Estar.

Haber is a true auxiliary because it helps to form compound tenses[1] but it presents the following peculiarities:

1. It is used as an impersonal verb (as well as the verb hacer which
is given here for the sake of completeness) for expressions of time,
as:

• Dos años ha (or ha dos años) or hace dos años la exportación de los Caldos españoles estaba muy floreciente.
  Two years ago the exportation of Spanish wines and oils was very flourishing.
• Ha dos años (or hace dos años) que la casa Guillermo Fernandez y Cía está establecida en La Coruña como Comisionistas.
  The firm, G.F. & Co., has been established in Corunna as Commission Agents these last two years.
• ¿Cuanto tiempo ha (or hace) que estudia V. el castellano?
  How long have you been studying Spanish?

2. It is also used impersonally as "there to be" (French, "y avoir"),
as:

• Hay mucha pimienta, clavos, y canela en el mercado de Londres.
  There are much pepper, cloves, and cinnamon in the London market.
• Sí, hubo muchas especias el año pasado también.
  Yes, there were many spices last year also.
• Cuando estaba en El Cairo había miedo de que estallara algún motín.
  When I was in Cairo there was the fear of some riots breaking out.

In English we have "there is" and "there are," because "there to be" is not used impersonally, the meaning being, e.g., "a man is there"; "two men are there." In Spanish, however, haber is used impersonally and both "there is a man" and "there are two men" are translated "Hay un hombre," "Hay dos hombres."

It will be noticed that Haber used for "there to be" makes Hay instead of Ha for the present indicative. All its other tenses remain unchanged: había, hubo, habrá, habría, etc.

Hay que followed by an Infinitive (French "il faut"), it is necessary to ..., as:

• Hay que tener mucho cuidado.
  It is necessary to be very careful. I, you,etc., must be very careful.

Tener is generally a principal (viz., not an auxiliary) verb, used to denote possession; but it is used sometimes as an auxiliary instead of haber, as:

• Tengo recibido su catálogo ilustrado y lista (or boletín) de precios.
  I have received your illustrated catalogue with price list.
• Tenemos recibida[2] su apreciable carta de 20 del que rige (or del corriente).
  We have received your favour of the 20th inst.
• ¿Tiene V. recibidas las cotizaciones?
  Have you received the quotations?
• Los presupuestos, que tenemos recibidos del Trapiche para nuestro Ingenio de la Habana.
  The estimates which we have received for the Sugar Mill for our Factory in Havana.

In all the preceding examples tener used instead of haber introduces an additional idea of possession.

"He recibido su carta" might be followed, in Spanish, by "pero la he perdido" (but I have lost it). "Tengo recibida su carta" implies that the receiver holds it now.

Sometimes this idea of possession is very distantly implied, as:

• ¿Qué me dice V.? tengo leído ese proyecto de Ley.
  What are you talking about? I have read that (Parliamentary) Bill.

Meaning that the effect of the reading is extant in the mind.

Colloquially the people will use tener for haber without any allusion to possession, but this should be avoided.