What is a classic fit button-up shirt?

It is a roomier cut than slim or tailored fits, with more space through the chest and waist. It sits straight over the body rather than hugging it.

Can I wear it under a sweater or jacket?

Yes. The full button front and plain design layer easily under a crewneck, cardigan or blazer. The long sleeves work under a jacket without bunching at the cuff.

Is it a dress shirt or a casual shirt?

It is a basic button-up that works both ways. Worn tucked with trousers it reads business-casual; worn open over a tee it reads casual.

How should I choose a size?

Go with your usual collar or chest size for a classic fit. If you want a closer fit, consider one size down, since the cut is roomy through the body.

What should I check before buying?

Look at the fabric content and care instructions, since those decide how it feels and how much ironing it needs. Check the sleeve and body length if you plan to tuck it in.