Strange masculine, singular forms
I don't know if it helps but I have noticed that the masculine, singular forms are irregular in certain groups. We all know that -o is usually a masculine letter, -a feminine and -s for the plural:
el, la, los las (el is not like the others) also the related aquél, aquélla, etc. (and the ones without the accent)
From uno: un, una, unos, unas (and alguno, ninguno) Strange one:un
este, esta, estos, estas: (remove the 't' for translating 'that': ese, esa etc...) este is the masculine, singular (esto is neuter)
So I suppose if you remember the masculine singular one, then the rest should be easier to work out just by putting on regular endings.
That's right, there are masculine words which do not finish at -o. For example, nouns ended at -ista: "un taxista" and "una taxista" (a male taxi driver and a female taxi driver).
However, I would not connect aquel/aquella/aquellos/aquellas with el/la/los/las despite having similar endings. In Spain we call them "determinantes demostrativos" (If they have a "tilde" -an accent-, they are pronouns instead of determiners). There are three types to show a distance in time or space:
1) Near: este/esta/estos/estas.
2) Intermediate distance (That/those are often translated as these): ese/esa/esos/esas.
3) Long distance: aquel/aquella/aquellos/aquellas.
There are also neuter singular pronouns: esto, eso and aquello. They do not have an accent (tilde) since there are not determiner versions to be distinguished from. The rest of these pronouns are: éste/ésta/éstos/éstas, ése/ésa/ésos/ésas and aquél/aquélla/aquéllos/aquéllas.
Oh yes, I know about el/aquel etc, it is just that I mean the endings are the same. I am just showing that in different parts of speech, the masculine singular ones are the ones with an irregular pattern