White Deadnettle (Lamium album)
The question is then, where, on all those pages do you start to look?
As with all wildlife, animal or vegetable, science has classified all living things into Kingdoms, Phylum, Classes, Orders, Families, Genera and Species (You can remember this by recalling that King Philip called out for garlic sausage!)
In other words, if you can decide on the order or the family then you know where to start looking.
The labiate family has some 40 species listed in my field guide over five pages. They all have square stems and tubular, trumpet shaped flowers. The flowers nearly always come as a whorl around the stem. They include mints, nettles, woundworts and bugles. All different yet all with similar features.
This is a photo of a plant with a square stem and tubular flowers in a whorl and can be quickly traced to the dead-nettles, in this case, as the flowers are white it's White Deadnettle.