When is a castle not a castle?

A castle is advertised for sale. So I took a look.

Cavers Castle (or maybe Cavers House?) in its prime.

Cavers Castle, a tower house of the Black Douglas, was destroyed by the English in 1545, remodelled in the 1750s and much extended in 1887. It has been a ruin since 1953 when the last Palmer Douglas laird, quite remarkably, sold the contents and allowed the army to use the building for target practice. Now mature spruce trees surround and oppress the sad skeleton, swaying arrogantly in what was drive, lawn, flower bed.

Cavers now.

I chatted to some people from a cottage nearby. "It's not really a castle", they said, "more of a mansion house". And when I looked in my favourite reference book, the entry under Cavers Castle read, 'See Cavers House'. 

So which is it?
The generally accepted definition of a castle is a 'private fortified residence'. When built in the 16th century Cavers was undoubtedly a castle; but in 1887 it was rebuilt for gracious living with no thought for defence. Queen Victoria and Prince Albert did not build Balmoral as a fortified residence in 1856 but, unlike Cavers, it does have many of the architectural defensive features of a castle.

Balmoral Castle.

Blair Castle, seat of the Dukes of Atholl, started as a castle, was remodelled in 1740 to be a stylish country house with no turrets or castellations then in the 1860s, under the influence of Balmoral, was transformed back into a castle!

So it is a grey area... which could confuse the potential castle purchaser. Or, more unfortunately, a visitor to our shores; Castle Venlaw in Peebles, for example, is a very good hotel, but no more a castle than your house or mine!