a pencil sharpener-pencil sharpeners
a picture-pictures
a workbook-workbooks
a paper clip-paper clips
a door-doors
a clock-clocks
a window-windows
a calendar-calendars
a pencil sharpener-pencil sharpeners
a picture-pictures
a workbook-workbooks
a paper clip-paper clips
a door-doors
a clock-clocks
a window-windows
a calendar-calendars