Cada huelga de obreros daña la industria nacional.
Each workmen's strike injures national industry.

Alguien, algo, cada, nada, nadie are invariable, and the verb accompanying them is always singular, as:

Alguien hizo un error de pluma.
Somebody made a slip of the pen.

Algo es mejor que el dinero, el honor.
There is something better than money, honor.

¿Hay algo peor que la ingratitud?
Is there anything worse than ingratitude?

Nada es absolutamente perfecto y nadie es infalible.
Nothing is absolutely perfect and nobody is infallible.

Further difference in meaning between alguien and alguno--

Alguien refers to persons only, and cannot be followed by de.
Alguno to persons or things, and may be followed by de,[2] as:

Alguien se ha quejado
Somebody has complained.

Alguno se ha quejado
Somebody has complained.

Quiere naranjas y melocotones y yo tengo algunos.
He wants oranges and peaches, and I have some.

Alguno de ellos lo hará.
Someone amongst them will do it.

The English "any," "anything," are translated by alguno, alguna cosa (algo) when interrogative; ninguno, ninguna cosa (nada) when negative; and cualquiera, cualquiera cosa when affirmative, as:

¿Quiere algún refresco ó algo que comer?
Do you want any refreshments[3] or anything to eat?

No quiero ningunos tacos.
I do not want any tacos.

Cualquier(a) muchacho echaría de ver que estas bombillas son más ordinarias.
Any kid could see that these light bulbs are of lower quality.

Alguno and Ninguno are left understood oftener than in English, as:

¿Comprará V. (algunos) títulos de la nueva emisión?
Will you buy any stock of the new issue?

Él no pide consejos.
He does not ask any advice.

When nadie and ninguno, or any other negative word, as the adverb nunca (never), etc., precede a verb, no other negative is required; but when they follow it, no (not) must precede the verb, as: No he visto á nadie or á nadie he visto: I have seen nobody.

These pronouns have four different forms and agree in gender and number with the nouns they modify.

Veo a algunos hombres. - I see some men.
Tiene mucha libertad. - He has a lot of freedom.

Cada is invariable - it is followed by a singular noun and the third personal singular verb form.

Cada país tiene sus proprias tradiciones. - Each country has its own traditions.
Quiero mirar cada coche. - I want to look at each car.

Tal has only singular and plural forms: tal, tales

No hay tal cosa. - There's no such thing.
Tales ideas nos ayudarán. - Such ideas will help us.

Varios has only masculine and feminine plural forms: varios, varias

Tengo varios libros. - I have several books.
Compré varias flores. - I bought several flowers.

Unlike most Spanish adjectives, indefinite adjectives precede the noun they modify.