Many of my online students have asked me to teach the correct use of 'could' - so here are the first 3 meanings. I'll send the final 3 meanings next week.

Could (modal verb) Part 1 Could (modal verb) Part 2Meaning 1: 'Could' is the past simple of 'can'. We use it to talk about what someone or something was able or allowed to do.Examples: When I was at school, I could swim much better than I can swim now.The exam was so difficult that I couldn't finish it. His mother said he could play football after he had finished his homework.Meaning 2: Could is used as a more polite form of 'can' when asking for permission. Examples: Excuse me, could I just interrupt for a moment, please? (note: this is much more polite than 'Can I interrupt, please'.)Hello, could I speak to Fiona Price, please? (note: this is what we say on the telephone.)Meaning 3: Could is used as a more polite form of 'can' when making a request.Examples: Could you please lend me your car for the weekend?Do you think you could possibly lend me fifty pounds (ё50) until Monday? (note: this is a more indirect question, and is therefore more polite.)Could you close the window, please?This week's proverb:He who pays the piper calls the tune.Meaning: The person who provides the money for something controls how it is spent.
Meaning 4: Expresses possibility, especially slight or uncertain possibility.Examples: She could leave at any time.This new drug could be an important step in the fight against heart disease.Be careful with that boiling water you could scald yourself!Meaning 5: We sometimes use could for making a suggestion Examples: We could go for a picnic tomorrow, if you like.You could always ask Tom to help you I don t think he would mind. (note: this means ' one option is to ask Tom to help you'.)Meaning 6: We use could to say, especially angrily, what we think someone else should do. In this case, could is emphasised strongly.Examples: Well, you could try to be a little more polite to my mother!I invited you ages ago you could have let me know sooner that you weren t coming!This week's proverb:Blood is thicker than water. Meaning: Family relationships are stronger than relationships with other people.I hope you enjoy this word study and your DailyStep audio lessons. Please email me at hussein10@mail.ru if you have any questions or suggestions.
Best wishes,Hussein Askerov  English teacher 
www.english-lectures.blogspot.com