Since Opera 10 gives it a very useful Opera to expand function to an extensive dictionary and while spell checking. For this click in a text box the right mouse button and select Add to Dictionary / Remove . Here you can either select the desired language.
A recommendable one version, however, is the following dictionary of the OpenOffice Extension website, this has a much larger stem. This is in the Opera profile directory in the subfolder / dictionaries unpacked. The file is indeed present in OpenOffice own format, but can still be opened with unpacking and unpacked. That was already a much more comprehensive spell checking is available to operators.
