Ask for clarification in a lecture

You are a student in Dr Smith's history lecture. He has just used the word 'urbanisation'. You do not understand it. Politely interrupt and ask him to (1) repeat the word, and (2) explain what it means. End by checking your own understanding of his answer. Remember: start with 'Excuse me' or 'Sorry', use 'could', and finish with 'please' or 'thank you'.