Sentience

This is a bug bear of epic proportions, mainly because it has so filtered into the media that it is literally IMPOSSIBLE to create any kind of sci-fi without making this basic elemental blunder.
The problem is that these two words do NOT mean the same thing, and the word SENTIENT is used pretty much exclusively where the word SAPIENT is required.

http://dictionary.reference.com/search?q=sentient
Summary: Sentient = Having sensation.

http://dictionary.reference.com/search?q=sapient
Summary: Sapient = Having wisdom.

Now, these two seem similar, but they're very different. Virtually every life form is sentient. Basically anything that can tell that it is different from other things around it has sentience. Mice are sentient life forms because they can sense that they're being prodded and know that it is by something that is not them. They understand that object A is a worm and can be eaten, and object B is a rock and cannot. They understand that both A and B are not part of itself.
Sapient species are those capable of wise thought, typically characterised as ABSTRACT thought.
If a man and a dog go to the top of an open mine shaft, and the man drops a glass ball and a steel ball, the man can deuce from his prior experience that it is likely that the glass ball will have shattered when it hits the mine floor, whilst the steel ball will quite likely be intact. The dog cannot do so, it would only be able to perceive this if it went down the mine and saw for itself first hand. That is assuming it was capable of understanding that the steel ball and the pile of broken glass represented the same items it saw at the top, which is unlikely.
This demonstrates the essential difference between the two concepts, man has shown SAPIENCE the dog merely SENTIENCE.

Now every time I hear someone on a sci-fi film or series ask something like 'Is there any sentient life?' they would be far better asking 'Is there any sapient life?' because the chances are very good that what he's really trying to find out is if there are any creatures down there we can talk to and get stuff from. The amount of times that question gets asked and the answer is 'No' followed by the cast wandering around whilst various critters waft around is staggering.

Two mildly relevant points; sapient creatures are by definition ALSO sentient, but the reverse is most certainly not true. The reason why we have the scientific classification Homo Sapiens is simply because we are the ONLY specie on this planet capable of the kinds of abstract thought that warrants being sapient. If one day we show that dolphins or chimps are also then they would be reclassified, probably something along the lines of 'Ceta Sapiens' or, er, 'Munky Sapiens'.

It drives me batty. Hopefully after you've read this you'll become massively intolerant of this same gratuitous misuse of English and campaign vocally for the mistake to never be repeated.