As þ is to t so is ð to d.
As ð is to d so is κ to k.
As κ is to k so is γ to g.
As γ is to g so is σ to s.
As σ is to s so is ζ to z.
Hence p, b, t, d, k, g, s, z, are lene; f, v, þ, ð, κ, γ, σ, ζ, are aspirate. Also p, f, t, þ, k, κ, s, σ, are sharp, whilst b, v, d, ð, g, γ, z, ζ, are flat; so that there is a double series of relationship capable of being expressed as follows:—
| Lene. | Aspirate. | Sharp. | Flat. | ||||
| Sharp. | Flat. | Sharp. | Flat. | Lene. | Aspirate. | Lene. | Aspirate. |
| p | b | f | v | p | f | b | v |
| t | d | þ | ð | t | þ | d | ð |
| k | g | κ | γ | k | κ | g | γ |
| s | z | σ | ζ | s | σ | z | ζ |
I am not familiar enough with the early grammarians to know when the terms lene and aspirate were first used. They were the Latin equivalents to the Greek words ψίλον (psilon) and δάσυ (dasy) respectively. The Greek terms are preferable. They convey no determinate idea, whereas the Latin terms convey a false one. The origin of the word aspirate I imagine to be as follows. The Latin language, wanting both the sound of the Greek theta, and the sign to express it (θ) rendered it by th. This orthography engenders the false notion that θ differed from τ by the addition of the aspirate h. To guard against similar false notions, I rarely hereafter use the word aspirate without qualifying it by the addition of the adjective so-called.
All the so-called aspirates are continuous; and, with the exception of s and z, all the lenes are explosive.