Most common errors when learning Italian Pt. 1, word gender

During my experience in teaching Italian as second language I've noticed - as it probably is "supposed to be" - that  students always make more or less the same errors.

Surfing on the internet I've searched for the most common difficulties in learning Italian to see if those made by  my students actually are widespread problems. I decided to share with you what I've found in a little series of writings. So, considering both my experience and what I've found in various articles on the web, these are probably the most common errors when learning Italian:  

1. Word gender

Differently to english, remembering word gender in italian is very important and a crucial grammatical rule. On first impression you may say that this is not so difficult: masculine nouns end in -o   - e.g. "letto" (bed) - and feminine in -a - "casa" (house). Well, unfortunately that's not completely right.  

First of all, there are a lot of masculine nouns that end in -a: problema (problem), pigiama (pajama), pirata (pirate); and there are also feminine nouns that end in -o: mano (hand), radio (radio) etc.

In addition, there are mascuiline nouns that end in -e like "presidente" (president), "attore" (actor) or "cantante" (singer). This group of nouns is actually a bit more hard to remember because there are different rules for their feminine  form, e.g. attore-->attrice, dottore-->dottoressa, cantante-->cantante (yes, it doesn't change), infermiere-->infermiera  

Due to these various rules on forming word gender, a common mistake when speaking italian is to failing in keep concurrence between nouns and articles, since in italian articles too have a gender. You can often hear a non-italian speaker saying things like "una problema" (a problem) but the article "una" is feminine, while "problema" is a masculine noun, so the correct way to say it is using a masculine article: "un problema".