The phrase "and difficult to characterize" is correct and usable in written English.
It can be used when describing something that is hard to define or categorize clearly.
Example: "The phenomenon was complex and difficult to characterize, leaving researchers puzzled."
Alternatives: "and hard to define" or "and challenging to describe".
But what is clear is how complex, consequential and difficult to characterize the new generation of large-scale philanthropy has become.
Restlessness may not be severe and difficult to characterize.
I note that selective environments are extremely complex and difficult to characterize; they may change, for example, seasonally, and/or through the course of an individual's pre-mating life, such that different pressures may "evaluate" individual fitness at different times.
Moreover, neural networks can predict the transport of heterogeneous and difficult to characterize water treatment contaminants such as natural organic matter and disinfection by-product precursors, whose physicochemical properties are unknown.
flow induced "blow-off" of previously deposited oil in the form of droplets is poorly understood, for one because the generated spectrum is very wide and difficult to characterize with temporal and size resolution, especially for very large drops which carry most of the mass.
Presenting features are often nonspecific and difficult to characterize.
Conversely, involuntary exposures from waste sites may be at low concentrations and hence difficult to characterize and quantify.
It is plausible that the relation between blood lead and blood pressure differs in childhood and adulthood, or that it is unstable in childhood, and thus difficult to characterize with one measurement.
The molecular events leading to these conformational changes and their effects on the overall mechanism are largely unknown and often difficult to characterize experimentally.
Despite decades of research, the mechanisms of pyrite formation are not sufficiently understood because solid and dissolved intermediates are oxygen-sensitive and poorly crystalline and therefore notoriously difficult to characterize and quantify.
Compared with geological disposal, near-surface disposal demonstrates a greater diversity of disposal system designs, a wider variety in hydrogeological settings, waste that is more heterogeneous in nature and more difficult to characterize than typical waste streams intended for geological disposal.
