Describe curves by words

Question

I am trying to describe the general aspect of the following curves

My ideas:

1. The curves are continuous, and defined for positive values of x, and giving negative values.
2. Have logarithmic growth (increase logarithmically)
3. The curves become flatten as they approaches the x axis.

Does any one have other ideas for describing such curves?

Please feel free to point me if the ideas I mentioned are not suitable for describing the curves.

Thank you in advance.