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Knowing when to use the preterite or imperfect tense when expressing a past action is one of the trickiest aspects of spanish grammar and can cause confusion for any level of spanish speaker. I always lik...

The two main past tenses in German are the simple past and the present perfect. The simple past uses just one word, for example 'ich ging', while the present perfect uses two words, for example 'ich bin g...

Enzymes are proteins. They are biological catalysts, meaning they increase the rate of reaction without being used up or changed. Different enzymes have different optimum temperatures and pHs, depending o...

The imperfect tense is a past tense. There are three reasons why we might use the imperfect tense and these can be remembered as: habitual, incomplete and descriptive. What does 'habitual' mean? Habitual ...

A 'non-specific' defence system means that its response is the same for every invader (pathogen). In the human body this includes:

Skin- a physical barrier between the outside worl...