theory, conditions, variables, equations, properties, analysis, constraints, relations, region, approximation, quantities, model, condition, considerations, approach, parameters, description, factors, method, limit, effects, factor, regions, cuts, data, range, viscosity, problems, structure, point, relativity, effect, theorem, relation, constraint, information, aspects, singularities, equation, assumptions, problem, characteristics, studies, reasons, theories, diffraction, concepts, relationships, behaviour, distributions, features, situation, domain, scattering, treatment, principle, configuration, result, models, results, principles, limits, hardening, interpretation, arguments, laws, calculations, relationship, regime, formulae, ideas, fit, age, behavior, quantity, space, configurations, origin, requirements, restrictions, descriptions, formulas, design, definition, images, theorems, reconstruction, conception, framework, velocity