The concept has its '''extension''' (it includes all beings with the same quality) and 'understanding' (a complex of markers referred to the idea). For example, the concept of ''pain'' refers to many human beings, but it is more generic (great extension, but little understanding). If we consider the pain in patients who receive, for example, dental implants, in patients with ongoing inflammatory dental pulpitis and patients with neuropathic pain (atypical odontalgia)<ref>{{cita libro | The concept has its '''extension''' (it includes all beings with the same quality) and 'understanding' (a complex of markers referred to the idea). For example, the concept of ''pain'' refers to many human beings, but it is more generic (great extension, but little understanding). If we consider the pain in patients who receive, for example, dental implants, in patients with ongoing inflammatory dental pulpitis and patients with neuropathic pain (atypical odontalgia)<ref>{{cita libro |