What does it mean to describe a weed as "invasive"?

That it came from another country, state or town. It is brought into somwhere it wasn't befrore and takes over the other areas of plants. Overgrows the other plants.

Explanation:

I dont'  have the exact definition but here it is summed up.

you should wear a lead protective shield when having teeth x-rays

hope i

-lavira : )

the answer is true when observing or determining population size, a direct observation is use, in which each organism is counted in a population or in an area. one benefit of this measure is that you get the exact population count but it will take a long time to  determine  the  size  of a  population.