Noun gender in Spanish
We know that most of the time, if a words ends in an "o" it's going to be a masculine word, and if it ends in an "a", a feminine word.
If a word has both endings to talk about men and women, then you're 100% sure about this.
However, by now we all now it's not as simple as it sounds.
First, a truth bomb:
Sometimes, you can't 100% sure and that's ok.
Experience and practice will give you the extra information you need.
Let's see some tips to make our guess as accurate as possible:
All numbers, days of the week and months.
El cinco - Five.
El jueves - (On) Thursday.
Noviembre es muy frío -November is very cold.
El sur es más caluroso - The South is hotter.
Usually, nouns related to geography are also masculine (rivers, lakes, volcanos, canals, parks, and the names of mountains).
El (río) Amazonas - The Amazonas (river).
El lago es profundo - The lake is deep.
El volcán es muy alto - The volcano is very tall.
En Amsterdam vi muchos canales - In Amsterdam I saw many canals.
Fuimos a los Pirineos - We went to the Pyrenees.
Finally, if it ends in a r or l, it's more likely to be masculine than feminine.
El rencor, el atril, el amor, el blancor, el temblor, el calor,el alcohol...
This includes the jobs that end in -or in masculine form like:
escritor, diseñador, revisor, traductor, profesor, proveedor, actor, adiestrador...
and also adjectives ending in -or:
acondicionador, acogedor, adulador, agitador,...
Letters are feminine: La a, la b, la c...
Words that end in -sión, -ción, -dad, -tad, -tud, and -umbre are also feminine.
La decisión, la conversación, la humildad, la libertad, la actitud, la incertidumbre...
Words that don't care
Most words that end in -ante/-ente will not have an option for each gender. You just use the article before the noun to specify:
El estudiante /La estudiante
El cantante / la cantante
El paciente / La paciente
There are other words, with different ending, with just one version:
El testigo / La testigo
Be extra careful with some jobs that end in a "o" or in a "a" for both genders, because those can lead to confusion:
El modelo / La modelo
El periodista / La periodista
El artista / La artista
El recepcionista / La recepcionista
El oficinista / La oficinista
El deportista / La deportista
El guía / La guía
Gender with animals
Same way as those jobs, some animals, usually those that are not considered pets, don't have two options.
In this case, you only use one of the articles with them ("el" or "la") and that doesn't change with the sex of the animal either.
La tortuga, el ratón, el elefante, el rinoceronte, ..."
Never El tortuga, la ratón...
However, you can clarify by saying: La tortuga hembra (the female turtle) and La tortuga macho (the male turtle) and that applies to any of these animals.
Words whose gender you'd never guess
These are some common masculine words that end in an "-a".
Notice that most of them end in -ma, which makes this a frequent ending for masculine words.