MeSH part I. Where can you find the meaning of "life"?

I found it in the MeSH database.

Really!

Looking for a quick answer? Don't ask a scientist
It doesn't take long to realize that scientists can spend countless hours debating the meaning of words. Our very own ScienceBlogs is a great example, just look at the many ways we can define (and debate) the meaning of a small, four-letter word like "gene". We also like to qualify our answers with a thousand conditions "usually, it's like this, but...."

This habit can be very frustrating if all you want is a quick concise answer.

On your marks, define that term!
So, many people turn to Google and Wikipedia for quick definitions. But Google sometimes lacks the nice reassurance of authority and often it seems like the pages we get simply copy each other.

Take the word "vector" that I defined the other day when I was bemoaning the lack of an intrascience dictionary and cursing those people in other fields who devise different meanings for words like "artifact."

Here's what I get when search Google for the definition of vector.

I can also find quite a few listings in Wikipedia for vector, although I haven't a clue what a "Truth Vector" in philosophy would be. Maybe Janet knows the answer to this one.

Ask a librarian!
Still, if you're a student working on an assignment, or just someone who wants a second opinion, it's nice to be able to reference some other kind of authority (at least for biology terms). Plus, if you need a definition for a class assignment, there are many college instructors and teachers who won't accept references from Wikipedia.

They may not accept Wikipedia, but I am certain that they will accept definitions from the NIH. After all, what could be more authoritative than the medical librarians at the National Institutes of Health?

You can find their definitions for terms in the MeSH database at the NCBI (National Center for Biotechnology Information).

MeSH is an abbreviation for Medical Subject Headings. It's used to provide a consistent and controlled vocabulary for organizing articles in the MEDLINE and PubMed databases.

I know that sounds kind of dull, but I really like the MeSH definitions for terms and the links to related terms. Plus the MeSH database is easy to use and it's a reference that you can trust because it's run by the people at the National Library of Medicine. I trust the medical librarians to do well with medical and scientific terms.

How do we find and use the MeSH database?
1. Go to the NCBI, http://www.ncbi.nih.gov

2. Choose MeSH from the list of databases in the pull-down menu.

Note: the list is NOT in alphabetical order, you just have to grit your teeth can read the headings.

3. Type a word in the search box and click the "Go" button.

What is the meaning of life?

MeSH has several things to say about meaning of life. Here's the top definition:

1. The state that distinguishes organisms from inorganic matter, manifested by growth, metabolism, reproduction, and adaptation. It includes the course of existence, the sum of experiences, the mode of existing, or the fact of being. Over the centuries inquiries into the nature of life have crossed the boundaries from philosophy to biology, forensic medicine, anthropology, etc., in creative as well as scientific literature. (Random House Unabridged Dictionary, 2d ed; Dr. James H. Cassedy, NLM History of Medicine Division) Year introduced: 1997

How does MeSH define a vector?
MeSH lists 8 types of vectors.

If we look at the definition for a genetic vector, we get:

DNA molecules capable of autonomous replication within a host cell and into which other DNA sequences can be inserted and thus amplified. Many are derived from PLASMIDS; BACTERIOPHAGES; or VIRUSES. They are used for transporting foreign genes into recipient cells. Genetic vectors possess a functional replicator site and contain GENETIC MARKERS to facilitate their selective recognition.
Year introduced: 1980

How does MeSH define a gene?
Genes:

Specific sequences of nucleotides along a molecule of DNA (or, in the case of some viruses, RNA) which represent functional units of HEREDITY. Most eukaryotic genes contain a set of coding regions (EXONS) that are spliced together in the transcript, after removal of intervening sequence (INTRONS) and are therefore labeled split genes.
Year introduced: 1965

I can live with that.