NEWICK is a simple format used to write out trees in a text file. While this is a hard-to-read format for humans, it is very useful for exchanging trees between different types of software. An example of the contents of a NEWICK format tree file is given below (note that semi-colon is needed to end the tree). Further information on this format can be found at Joe Felsenstein’s website.
((raccoon, bear),((sea_lion,seal),((monkey,cat), weasel)),dog);
The above tree with branch lengths will look as follows:
((raccoon:19.19959,bear:6.80041):0.84600,((sea_lion:11.99700, seal:12.00300):7.52973,((monkey:100.85930,cat:47.14069):20.59201, weasel:18.87953):2.09460):3.87382,dog:25.46154);
If you wish to specify bootstrap values then they could appear before the branch lengths (e.g., in .dnd files produced by CLUSTAL) or after the branch lengths (e.g., in .PHB files produced by CLUSTAL). In these cases, the format might look like:
((raccoon:19.19959,bear:6.80041)50:0.84600,((sea_lion:11.99700, seal:12.00300)100:7.52973,((monkey:100.85930,cat:47.14069)80:20.59201, weasel:18.87953)75:2.09460)50:3.87382,dog:25.46154);
or
((raccoon:19.19959,bear:6.80041):0.84600[50],((sea_lion:11.99700, seal:12.00300):7.52973[100],((monkey:100.85930,cat:47.14069):20.59201[80], weasel:18.87953):2.09460[75]):3.87382[50],dog:25.46154);