no idea where you tried to download it from but artha is already in ubuntu's repositories so you don't need a different download to install it.
things that get installed from the repo's do not show up as a download in the download folder.
if you want to use the latest and greatest then you will need to add a repo (ppa) to install it from or download the .deb (which will be downloaded to the downloads folder.) and install that. it's the amd64.deb you need.
Linux Debian & family
If you are using Debian or its derivatives like Ubuntu, Kubuntu, Xubuntu, etc. then Artha is already available in the repositories. You can install it by:
$ sudo apt-get install artha
Both Debian and Ubuntu has the version 1.0.2 of Artha in their respective repositories; so by installing using the above command, you'll not get the latest 1.0.3 release. Hence if you prefer to have the latest version, there are two options available ~ PPA and direct .deb download.
Artha now has a PPA in launchpad. This can be added to your system's repository sources through
$ sudo apt-add-repository ppa:legends2k/artha
This will prompt you to accept adding the PPA's keys to your system. Accept it by pressing RETURN. Once this is done, update the package data and install Artha.
$ sudo apt-get update
$ sudo apt-get install artha
Alternatively, you can also download the deb file below for your architecture and install the same (instructions below). This is more of a manual method and the PPA method is encouraged over this one, since this method lacks automatic updation of the package, should there be a newer version of Artha.
Architecture Binary i386 artha_1.0.3-1_i386.deb AMD64 artha_1.0.3-1_amd64.deb
NOTE: Please use gdebi to install this deb package. Do not use dpkg, since it does not have the ability to automatically resolve dependencies and will lead to broken dependencies. Should you end up in broken dependencies give sudo apt-get install -f to resolve it; apt will take care of fixing it. On most Debian based distros, gdebi-gtk (GUI front end of gdebi) comes pre-installed. If you have it installed, you can simply double click the downloaded .deb file and gdebi will show you a graphical interface to install Artha. Follow the instructions and it will install Artha resolving dependencies. If you go by the CLI way:
$ sudo gdebi artha_1.0.3-1_i386.deb
Make sure the Universe repositories are enabled in your repositories list for gdebi will look for WordNet which is available only in the Universe.
personally i'd try it first from the repo. (just checked and it's version 1.0.3 that gets installed anyway so i'd stick to this way.)
do you still get the spinning icon when you click on the orange folder, ubuntu software icon?
if not and it opens like it should then click on that, then search for artha, click on the search result then click on the install button, enter your password and then it will install it.
you will then find it in the taskbar on the left, just click it to open and use.
not sure it's the best one to use though because it doesn't seem to have been updated since 2012 so there are probably better apps that are still updated.
have you looked into libreoffice and what thesaurus and dictionary, spell checkers etc that can be used with that?
it might be all you need.
Edited by terry1966, 14 June 2016 - 12:06 PM.