A lot
Use for 'quite a lot' or 'plenty'. It implies a sufficient or considerable amount.
An informal way to say 'a ton' or 'a bunch'. Very common in casual conversation.
Use for 'too much' or 'too many'. This implies an excessive, often negative, amount.
I have a lot of work today.
My brother eats a lot.
There are a ton of people in the park.
Thank you, but it's too much. I can't eat more.
The apartment is quite large.
'Mucho' is the universal word for 'a lot' or 'much' and is understood everywhere. 'Un montón' is also widely used informally across Latin America and Spain.
The very informal slang 'mogollón' is extremely common to mean 'a ton' or 'loads', used in the same way as 'un montón'.
Besides 'un montón', the colloquial expression 'un chorro' is frequently used to mean 'a lot', as in 'cuesta un chorro' (it costs a lot).
The informal phrase 'una bocha' is very common in everyday speech to say 'a lot', for example, 'hace una bocha de calor' (it's really hot).
You will often hear the informal word 'un pocotón' (a blend of 'poco' and 'montón') to express a very large quantity.
Confusing 'mucho' and 'muy'. Use 'muy' before adjectives (muy grande - very big). Use 'mucho' after verbs (trabajo mucho - I work a lot) or before nouns (mucho tiempo - a lot of time).
Forgetting to match gender and number. 'Mucho' changes to match the noun: 'mucha agua' (a lot of water), 'muchos carros' (a lot of cars), 'muchas gracias' (many thanks).
Translating 'a lot of' literally as 'un lote de'. This is incorrect. 'Un lote' is a 'batch' or a 'plot of land'. Always use 'mucho/a/os/as'.