FocusWriter is a lightweight word processor. Here's how you can install it in Ubuntu 14.04.
1. Open a terminal window.
2. Type in the following commands then hit Enter after each:
sudo add-apt-repository ppa:gottcode/gcppa
sudo apt-get update
sudo apt-get install focuswriter
FocusWriter offers the following features:
TXT, basic RTF, and basic ODT file support
Timers and alarms
Fully customizable themes
Typewriter sound effects (optional)
Live statistics (optional)
Portable mode (optional)
Translated into over 20 languages
According to Noobs Lab:
FocusWriter allows you to skin your environment by creating themes that control the font, colors, and background image to add ambiance. It also features on-the-fly updating statistics, daily goals, multiple open documents, spell-checking, and much more.
The interface is there when you want it and vanishes into the background when you just want to write. It does not require many system resources, it has a good response time and there are enough options to keep you busy for quite a while.More at Noobs Lab
Additional resources for FocusWriter
Additional Ubuntu resources