「このごろ」と「このあいだ」 kono goro vs. kono aida

「このごろ」 "kono goro" means "these days", while 「このあいだ」"kono aida" means "the other day". That is, "kono goro" refers to something which has been going on for a while, while "kono aida" is used for a particular event that occurred recently.

「～ばいい」と「～たらいい」と「～といい」

～ば, ～たら and ～と are all conditionals. They are not always interchangeable, as I have written here. But what does it mean when they follow the adjective いい "ii"?

The word for "world": "sekai" and "yononaka"「世界」と「世の中」の違い

The Japanese have many words for the word "world". However, they are not exactly interchangeable.

世界 "sekai" is commonly used for the physical world composed of the different countries and continents. In terms of nuance, it is related to 地球 "chikyuu", which literally means "the earth". Basically, 世界 can exist even without us human beings. Here are some real-life examples that come from some documentaries I've watched or from jisho.org.

世界選手権
sekai senshuken
World Championships

世界の頂点
sekai no chouten
top of the world

世界には7大陸がある。
Sekai niwa nanatairiku ga aru.
There are 7 continents in the world.

愛の力は世界を動かす。
Ai no chikara wa sekai wo ugokasu.
Love makes the world go round.

世の中 "yononaka", on the other hand, is used to refer to society instead of the "physical" world that 世界 is often used for. It is related to words like 世間 "seken" and 社会 "shakai", which both mean "society". (More on those two words later."

世の中は狭いものですね。
Yononaka wa semai mono desu ne.
It's a small world, isn't it?

彼は世の中を正気に戻した。
Kare wa yononaka wo shouki ni modoshita.
He brought the world back to its senses.

It seems though that there is some overlap, based on example sentences:

僕は新世界の神となる。
Boku wa shinsekai no kami to naru.
I will become a god of the new world. (from Death Note)


References:"Essential Japanese Vocabulary" by Akira Miura
jisho.org (for the example sentences)
http://detail.chiebukuro.yahoo.co.jp/qa/question_detail/q1088088560
http://okwave.jp/qa/q4404083.html

The word for "improve": "joutatsu" and "koujou"「上達」と「向上」

Eijiro gives the following words for "improve": joutatsu suru 「上達する」and koujou suru 「向上する」. However, they are not identical and I've done some research on the difference.

Let's start with the sample sentences from jisho.org (which uses the Tanaka corpus):

君の英語は上達している。
Kimi no Eigo wa joutatsu shite iru.
Your English is improving.

彼の英語力は著しく向上した。
Kare no Eigoryoku wa ichijirushiku koujou shita.
His English abilities have remarkably improved.

Note that joutatsu was used with Eigo, while koujou was used with Eigoryoku. This gives us one difference between the two: for 上達, what is relevant is the thing which is being improved on (in this case, English), while for 向上, it refers to something that goes "up" -- in this case, it is the English ability, and not English the language per se. If we say

英語は著しく向上した。
Eigo wa ichijirushiku koujou shita.
English (the language) has remarkably improved.

then we get a completely different meaning.

In some cases (like English ability), 上達 and 向上 can both be used with a minor change in sentence construction. However, in some cases, only one of the verbs can be used. 上達 is used for things where you can improve with practice, like sports, language abilities, piano skills, etc. 向上 has a wider scope, and includes improvements in condition, living standards, production, etc.

Here's a thread (in Japanese) about the same question. One of the replies says that 上達 means to "get better at something", while 向上 is more like "to advance in a good direction".

Reading practice: children's newspapers

Fortunately, some Japanese newspapers do release children's versions, such as the Yomiuri Shimbun and NHK News. This is great for practicing your kanji and increasing your vocabulary.

1. NHK News Web Easy
http://www3.nhk.or.jp/news/easy/

This one has furigana all over. Some people don't like it, but I do. I can read the kanji that I know without looking at the furigana, and then I just check the furigana after I finish guessing the reading. Also, the articles here are more recent. Best of all, this has AUDIO, so you also get to practice your listening skills as well!

2. Yomiuri Shimbun
http://www.yomiuri.co.jp/nie/note/kids/index.html

The nice thing about the Yomiuri kids' edition is that you can find articles by grade level. So if you're only confident about your kanji level being 3rd grade, then you can still read articles that don't require higher level kanji. Kanji that at are above your grade level are spelled out in furigana.