Regular, normal and ordinary have a very similar meaning, which is probably: ‘how you expect something to be, not unusual or special’. So if we had a normal or ordinary day at work, it would mean that nothing particularly special happened. A normal or an ordinary meal in a restaurant doesn’t sound very exciting, but I suppose it’s better than having an awful one! You can order a 'regular' coffee in a cafe or have a regular workout each day. There is a slight nuance in meaning, however, when we talk about normal people and ordinary people. If we mention normal people, it probably means ‘people who think and behave in the same way as most other people’. But the phrase ordinary people may carry a nuance in meaning about wealth and social status, meaning ‘people who are not particularly rich’. So we might say: These houses have been built for ordinary people to buy.