Thick describes something with a lot of distance between its opposite sides. A thick book has many pages, so the distance from the front cover to the back cover is substantial. A thick slice of bread is much taller than a thin slice. A thick tree trunk might take two people with outstretched arms to reach around it.

Thick can describe liquids that flow slowly because they're dense and heavy. Honey is thick; it pours slowly and coats your spoon. Thin liquids like water flow quickly and easily. When you make hot chocolate, adding more powder makes it thicker and more satisfying.

The word also describes things packed closely together. Thick fog makes it hard to see because water droplets fill the air densely. A thick forest has trees growing close to one another, creating deep shade. If you have thick hair, each strand grows close to its neighbors, creating a full, healthy look.

Sometimes thick describes a strong accent that's hard to understand, like when someone speaks English with a thick Russian accent. You can also say the air is thick with tension when everyone in a room feels uncomfortable and awkward.