When should you use the present subjunctive tense

There are many different uses for the subjunctive tense or 'congiuntivo' however it is most commonly used when the speaker or writer is expressing uncertainty or doubt instead of a fact. The subjunctive often follows phrases such as 'penso che', 'credo che' and 'è possibile che'. For example the present tense would be used if the speaker were to say 'The car is blue,' - 'La macchina è blu'. This is because the speaker in this example is certain that the car is blue and is stating a fact.However the subjunctive or 'congiuntivo' would be used if the speaker were to say 'I think the car is blue' - 'penso che la macchina sia blu'. The reason the subjunctive is used here instead of the present tense is because the speaker is expressing uncertainty. Be careful using subjunctive in this case however and do not confuse it with the conditional- which would be used in hypothetical situations. For example instead of using 'I think the car is blue', you could say 'the car could be blue' - 'la macchina potrebbe essere blu'. In this case the conditional is used as it is a hypothetical response rather than an expression of doubt.