Y - Yard
A Yard, like a Meter is how fabric is measured, I don't work in Yards so i use a conversion chart on Google to change Yards to Meters. You may work better in Yards its just what you feel comfortable. When your out shopping for fabric just bear the conversion in mind so you get what you need.
Z - Zip
A Zip like a Button and a Press Stud can be used as an embellishment detail or a closure.
There's 2 main types of zip, Invisible and the regular zip 'Visible'. If your pattern require an invisible zip you will need to buy a special foot for your machine. 'Visible' zips are great for Pencil Cases, Cushion Covers.
That's the end of my Sewing Dictionary series, I hope you find it helpful and It helps you on your Sewing Journey.